Ukraine is back in full control of its second-largest city of Kharkiv after an earlier advance by Russian forces, the regional governor said.
"Control over Kharkiv is completely ours," Oleh Sinegubov wrote in a Telegram message.
"The armed forces, the police, and the defence forces are working and the city is being completely cleansed of the enemy."
Journalists on the ground reported that without having eyes on the entire city, it appeared Ukraine had control of Kharkiv.
Fighting broke out in the streets of the north-eastern city between Ukrainian forces and Russian troops on Sunday and civilians were told not to leave their homes.
Videos posted on Ukrainian media and social networks showed Russian vehicles moving across Kharkiv and a light vehicle burning on the street.
A series of blasts were heard to the west of Kyiv's centre on Sunday minutes after air-raid sirens sounded in the capital, a Reuters correspondent said.
Ukrainian media reported explosions and a gunfight in a nearby town, including that a bridge has been blown up near the town of Bucha, west of Kyiv.
It was unclear whether it had been bombed by Russian troops or destroyed by the Ukrainian side.
Anton Herashchenko, an adviser to Ukraine's Interior Minister, said fighting was underway in Bucha against Russian forces trying to advance towards Kyiv.
Russian troops advance on key ports
Russian troops squeezed strategic ports in the country's south on Sunday.
The pressure appears to be aimed at seizing control of the country's coastline stretching from the border with Romania in the west to the border with Russia in the east.
A Russian Defence Ministry spokesman said Russian forces had blocked the cities of Kherson on the Black Sea and the port of Berdyansk on the Azov Sea.
He said the Russian forces also took control of an air base near Kherson and the Azov Sea city of Henichesk.
Cutting Ukraine's access to its sea ports would deal a major blow to the country's economy.
It could also allow Moscow to build a land corridor to Crimea, which Moscow annexed in 2014.
Zelenskyy still up for talks with Russia, but not in Belarus
Ukrainian President Volodymyr Zelenskyy said his country was ready for peace talks with Russia, but he had declined to meet with Russian officials in Belarus.
Mr Zelenskyy said Minsk was complicit in the Russian invasion.
The Kremlin said on Sunday that a Russian delegation, including military officials and diplomats, had arrived in the Belarusian city of Homel for talks with Ukrainian officials.
But Mr Zelenskyy made it clear he did not accept Russia's location selection and named Warsaw, Bratislava, Istanbul, Budapest or Baku as alternative venues.
Mr Zelenskyy earlier welcomed an offer from Turkey and Azerbaijan to organise diplomatic efforts.
He also offered to negotiate a key Russian demand — abandoning Ukraine's ambitions to join NATO.
Ukraine's Health Minister reported on Saturday that 198 people, including three children, had been killed and more than 1,000 wounded.
It was unclear whether those figures included both military and civilian casualties.
The President's office said there had been another explosion at the civilian Zhuliany airport.
Mr Zelenskyy's office also said Russian forces blew up a gas pipeline in Kharkiv, prompting the government to warn people to protect themselves from the smoke by covering their windows with damp cloths or gauze.
Officials have urged residents to stay away from windows to avoid flying debris and bullets as Russia's troops close in on Kyiv.
Residents there have sought safety inside and underground, and the government has implemented a 39-hour curfew to keep people off the streets.
Shelves are sparsely stocked at some grocery stores and pharmacies, and people are worried about how long food and medicine supplies may last.
More than 150,000 Ukrainians have fled for Poland, Moldova and other neighbouring countries, and the United Nations has warned the number could grow to 5 million if the fighting escalates.
Mr Zelenskyy has vowed his pro-Western country will not be bowed by Moscow.
"I am here. We will not lay down any weapons. We will defend our state because our weapons are our truth," Mr Zelenskyy said.
Ukraine says 200 Russian soldiers captured, thousands killed
The fighting on the outskirts of Kyiv appears to suggest small Russian units are trying to clear a path for Moscow's main forces.
Small groups of Russian troops were reported inside the city, but Britain and the US said the bulk of the forces were 30 kilometres from the city's centre.
Russia has said its forces assaulting Ukraine from the north, east and south are focusing only on military targets, but bridges, schools and residential neighbourhoods have been hit.
A missile struck a high-rise apartment building in Kyiv's south-western outskirts near one of the city's two passenger airports, leaving a jagged hole of ravaged apartments over several floors.
A rescue worker said six civilians were injured.
Ukraine's ambassador to the US, Oksana Markarova, said troops in Kyiv were fighting Russian "sabotage groups".
Ukraine said about 200 Russian soldiers had been captured and 2,800 Russian soldiers had been killed, without providing evidence.
Moscow was yet to report on casualties.
Ms Markarova said Ukraine was gathering evidence of shelling of residential areas, kindergartens and hospitals to submit to The Hague as possible crimes against humanity.
Highways into Kyiv from the east were dotted with checkpoints manned by Ukrainian troops and young men in civilian clothes carrying automatic rifles.
Low-flying planes patrolled the skies, but it was unclear if they were Russian or Ukrainian.
US, Germany send military aid to Ukraine
It was the fourth day since Russian President Vladimir Putin unleashed a full-scale invasion that has sparked fears of a wider conflict in Europe.
Mr Putin has not disclosed his ultimate plans, but Western officials believe he is determined to overthrow Ukraine's government and replace it with a regime of his own, redrawing the map of Europe and reviving Moscow's Cold-War-era influence.
It is unclear how much territory Russian forces have seized or how much their advance has been stalled.
Mr Zelenskyy has asked UN secretary-general António Guterres to strip Russia of its vote at the UN Security Council as punishment for invading Ukraine.
Russia is one of the five permanent members of the Security Council, which gives them the right of veto over any substantive draft resolution, even if they are the only dissenter.
Britain's Ministry of Defence said: "The speed of the Russian advance has temporarily slowed likely as a result of acute logistical difficulties and strong Ukrainian resistance."
A senior US defence official said more than half of the Russian combat power that was massed along Ukraine's borders had entered the country and Moscow had been forced to commit more fuel and support units inside Ukraine than originally anticipated.
To aid Ukraine's ability to hold out, the US has pledged an additional $US350 million ($484.35 million) in military assistance to Ukraine, including anti-tank weapons, body armour and small arms.
Germany said it would send missiles and anti-tank weapons to the besieged country and would close its airspace to Russian planes.
The US, EU and UK agreed to block "selected" Russian banks from the SWIFT global financial messaging system, which moves money around more than 11,000 banks and other financial institutions worldwide, as part of a new round of sanctions aimed to impose a severe cost on Moscow for the invasion.
They also agreed to impose "restrictive measures" on Russia's central bank.
The US and its allies have beefed up forces on NATO's eastern flank but so far have ruled out deploying troops to fight Russia.
Dmitry Medvedev, the deputy head of Russia's Security Council, warned that Moscow could react by opting out of the last remaining nuclear arms pact, freezing Western assets and cutting diplomatic ties.
"There is no particular need in maintaining diplomatic relations," Mr Medvedev said. "We may look at each other in binoculars and gun sights."
Mr Putin sent troops into Ukraine after denying for weeks that he intended to do so, all the while building up a force of almost 200,000 troops along the countries' borders.
He says the West has failed to take seriously Russia's security concerns about NATO, the Western military alliance that Ukraine had aspired to join.
He has also expressed scorn about Ukraine's right to exist as an independent state.
ABC/wires
