A viable explosive device has been discovered in Londonderry close to an area where children were playing football.
The device was discovered during a major security operation which followed an attempted hijacking in the city on Friday.
Four arrests have been made.
Police remain at the scene of the security alert in the Corrody Road.
On Friday night, police received a report that a delivery driver had been approached by three masked men armed with knives and a firearm.
The suspects ran off towards Corrody Road.
Police and ammunition technical officers attended the scene following the discovery of the suspicious object on Saturday.
Derry City and Strabane Area Commander, Chief Superintendent Nigel Goddard said it has now been declared viable and has been taken away for further examination.
He said: “A number of cordons remain in place as police continue to search the area as part of our investigation.
“We would like to thank the local community for their patience and understanding during this time.
“This explosive device was recklessly left in a public area, just metres away from houses and a sports area where a number of children were playing football.
“Four people have been arrested and a number of searches have been carried out by detectives investigating this incident and an attempted hijacking on Friday evening.
“They remain in custody assisting us with our inquiries.”
Mr Goddard added: “Our focus remains firmly on keeping people safe against the threat posed by violent groups.
“No matter what level of involvement people have with any criminal or terrorist activity, we will investigate and where appropriate, put people before the courts to answer for their actions.
“Our investigation into this incident is ongoing, and we strongly urge anyone with information, suspicions or concerns about dangerous and illegal activity in our community to contact us on 101.”
Detectives conducted a number of searches of properties in the area on Saturday. A number of items were seized and three men aged 54, 29 and 32 were arrested under Section 41 of the Terrorism Act 2000.
Police later said a fourth man, aged 34, had also been arrested.
A number of previous terrorist-related incidents in the north-west have been blamed on the dissident republican New IRA group.
