The head of the Police Service of Northern Ireland has asked for funding to recruit 800 officers to help deal with an increase in paramilitary activity in the region.

Simon Byrne said the force had had to deal with more callouts and investigations of terrorist threats since he took up the role in July than his predecessor had faced in the previous year.

“We can’t keep working at the pace we have done across the summer dealing with a rise of this kind of attack as well as day-to-day policing issues,” he said.

He has spoken to the Northern Ireland secretary, Julian Smith, about the need for more police.

Byrne was speaking in Derry after a bomb was discovered this week in the Creggan area of the city. Journalist Lyra McKee was murdered in the same area in April while observing clashes between a dissident republican group, the New IRA.

It was the second device found in less than a week after a mortar bomb was found near a police station in the nearby town of Strabane on Saturday.

“I’ve been very clear that we need to grow the PSNI to that figure of 7,500 officers so that we can push more police officers to work with communities to get more information to deal not only with day-to-day crime but to continue the fight against paramilitaries and terrorism,” Byrne said.

Police said on Saturday they were concerned with the number of devices left recklessly near residential and public areas.

After the discovery in Strabane, Supt Gordon McCalmont said: “The key concern is … not just by the New IRA but other groupings, we are seeing devices left at bus stops in other parts of Northern Ireland and these devices left in vulnerable positions for extended periods of time with absolute disregard for the community – it is absolutely frightening.”

Byrne said he was concerned that some more experienced terrorists were now involved with groups such as the New IRA, giving them an increased capability.

“It is a worrying departure in terms of the determination, the tempo and the motivation of people to clearly kill or seriously injure one of our officers,” he said.

“I am worried that the valiant efforts of officers cannot continue at this rate without support from the government to increase the number of people that I can deploy to communities to fight terrorism.”