Tensions between nuclear-armed rivals India and Pakistan have escalated over the disputed region of Kashmir, with Islamabad saying today it shot down two Indian warplanes and captured two pilots.
The civil aviation authority in Pakistan later shut all airspace in the country to commercial flights.
It came just hours after Pakistan said mortar shells fired by Indian troops from across the frontier dividing the two sectors of Kashmir killed six civilians and wounded several others.
But how have relations between the two nations deteriorated and what is at stake in the rapidly worsening conflict?
What we know so far on the latest tension
Pakistan's army spokesman Major General Asif Ghafoor said Pakistani troops on the ground captured the pilots. He added that one of the downed planes crashed in Pakistan's part of Kashmir, while the other went down in Indian-controlled section of the Himalayan region.
The injured pilot is being treated at a military hospital. Maj Gen Ghafoor said the pilots are being treated well, but made no mention of them being returned to India.
Indian air force spokesman Anupam Banerjee in New Delhi said he had no information on Pakistan's statement.
Meanwhile, the foreign ministry in Islamabad said the country's air force was carrying out air strikes from within Pakistani airspace across the disputed Kashmir boundary, but that this was not in "retaliation to continued Indian belligerence".
The disputed territory is split between Pakistan and India and claimed by both in its entirety.
Though Pakistani and Indian troops in Kashmir often trade fire, the latest casualties came a day after tensions escalated sharply following a pre-dawn air strike and incursion by India that New Delhi said targeted a terrorist training camp in north-western Pakistan.
What started the tensions?
The latest wave of tensions between the two countries erupted after militant group Jaish-e-Mohammed, which is based in Pakistan, claimed responsibility for a suicide bombing of a convoy of India's paramilitary forces in the Indian portion of Kashmir which killed 40 Indian troops on February 14.
The suicide bomber was from Indian Kashmir. New Delhi long has accused Pakistan of cultivating such groups, something denied by Islamabad.
Pakistan said it was not involved in the attack and was ready to help New Delhi in its investigations.
India launched an airstrike on Pakistani territory early on Tuesday that New Delhi called a pre-emptive strike against militant camps in Pakistan.
India said its bombs killed a "very large number" of militants, while Pakistan said there were no casualties in an airstrike it described as being carried out "in haste."
Why is tension dangerous?
Both India and Pakistan are believed to possess more than 100 nuclear warheads each and have conducted atomic weapon tests. Both countries have test-fired nuclear-capable missiles.
The Bulletin of Atomic Scientists warns that "computer models have predicted that the physical impacts of a nuclear exchange between India and Pakistan, or even a single strike on a large city, would be devastating and would reverberate throughout the world."
How did the dispute over Kashmir begin?
When Britain granted independence to the region in 1947, it divided the Indian subcontinent into a predominantly Hindu India and mostly Muslim Pakistan.
Some areas could decide their own fate and choose to accede to India or Pakistan. In Kashmir, the only Muslim majority area ruled by a Hindu monarch, its ruler was indecisive and wished to join India or for independence. This started the first India-Pakistan war in 1947.
The conflict ended in 1949 when a United Nations resolution established the Line of Control dividing Kashmir between the two nations and calling for a direct vote on which country should control it.
That vote has never been held. Indian and Pakistan fought a second war over Kashmir in 1965.
What has happened since?
India and Pakistan fought a third war in 1971 over what was East Pakistan, which later became Bangladesh.
In 1999 and 2000, after Pakistan's military sent a ground force into Indian-controlled Kashmir at Kargil, the two countries faced off and a worried world urged both to pull back from the brink of war, fearing it could escalate into a nuclear conflict.
Even in times of relative peace the two nations readily engage in brinkmanship and aggressive rhetoric.
How is Pakistan reacting?
Pakistan, which has a history of military coups and strong-arm rule from those tied to its intelligence services, has largely reacted to this conflict through its civilian government.
Foreign Minister Shah Mahmood Qureshi took the lead to condemn the airstrike on Tuesday, painting India as an aggressor who would suffer repercussions, without elaborating.
Qureshi also accused Indian Prime Minister Narendra Modi of playing with regional stability to get votes in upcoming national elections.
Prime Minister Imran Khan has called for a joint meeting of Pakistan's upper and lower houses of parliament. Public criticism of India has been loud across Pakistani media, with sporadic protests against New Delhi breaking out across the country.
How is India reacting?
Indian government officials called the airstrike on Tuesday a counterterrorism operation based on credible intelligence that another attack against India was imminent.
The tensions could be a boon for Modi, whose Hindu nationalist Bharatiya Janata Party aims to maintain power in the upcoming elections.
The airstrike appears to have temporarily insulated the Modi government from criticism about it failing to create as many jobs as pledged in the 2014 elections.
Opposition party leaders have responded with support for India's air force. Meanwhile, Modi earned points with the powerful Hindu nationalist social group, the Rashtriya Swayamsevak Sangh, or RSS.
RSS chief Mohan Bhagwat said Tuesday: "Truth and non-violence are fine, but the world understands the language of power."
