Army base bombs left 20 metres from homes
Police have said two bombs found close to an Army Reserve centre in Londonderry were left about 20 metres from nearby homes.
The devices were left at the perimeter fence of the Caw Camp Army base and were discovered at 11:00 BST on Monday.
The two bombs partially detonated.
About 15 homes in Caw Park and Rockport Park were evacuated during the security operation which ended on Monday evening.
Police said the bombers had endangered lives in the built-up residential area.
Police said CCTV footage indicated the devices detonated at about 23.35 BST on Sunday but failed to fully explode.
Ch Insp Tony Callaghan said the bombs were "clearly designed to kill or seriously injure".
"It was absolutely reckless for someone to leave these devices at the perimeter fence line of an Army reserve base in such close proximity to a number of properties," he said.
"This area is populated and there are a number of elderly residents living in the area and anyone could have been walking past at that time of night.
"There are elderly people too with Alzheimer's.
"The CCTV footage shows a flash and that footage is key to our investigation.
"I'm not aware at this stage if the footage shows anyone coming or leaving the area.
"Our main line of inquiry would be into dissident republican activity.
"It's common that dissidents like to raise their profile around election time but we will not let them take away from the good work we do."
The senior officer said two separate devices had been found and were probably part of one bomb.
The army reserve base backs onto houses in Rockport Park.
Houses in Caw Park were also evacuated during the bomb disposal operation.
Residents in nearby houses spent almost 10 hours out of their homes while the devices were made safe.
Anne Moffatt has lived in Rockport Park for more than 30 years and told BBC Radio Foyle the alert had caused significant disruption and upset for residents in the area.
Her house is next to where the police cordon was erected. She was allowed to remain in her home during the operation, but her neighbours had to leave.
"There was one elderly couple and the wife has Alzheimer's and the man in his eighties, and they've been out of their houses since [Monday] morning. I just think it's dreadful really," she said.
Ms Moffatt said those responsible "don't care about anybody".
"It just makes people nervous, the idea that people have been walking about here and watching things, it's a horrible feeling."
Other residents did not want to speak on radio, but said the event had brought back bad memories of a fatal bomb attack at the base 13 years ago.
David Caldwell was killed after picking up a lunch box packed with explosives in what was then known as a Territorial Army base in 2002.
Mr Caldwell, a 51-year-old father of four, had been involved in refurbishing facilities at Caw Camp.
The 2002 attack was carried out by the Real IRA.