They were detained in a major security operation involving up to 200 officers.
Mr Kerr, 25, a Catholic member of the Police Service of Northern Ireland, was killed when a booby-trap bomb exploded under his car outside his home in Omagh, Co Tyrone, on April 2.
Police confirmed that five men had been detained in connection with the murder and associated incidents.
Searches were also carried out in Coalisland, Co Tyrone, and Toome, Co Antrim, as well as Bellaghy and Ballyronan, south Derry.
One man from Omagh has already been charged in connection with the police investigation into Mr Kerr’s murder.
All five suspects held were arrested under the Terrorism Act and have been taken to Antrim police station for questioning.
A number of items were seized at the search locations, including clothing, mobile phones, computers and vehicles. They have been removed for forensic examination and analysis.
One man, aged 22, was detained in Coalisland. A second, aged 27, was arrested in Toome, a third, aged 37, in Bellaghy and a fourth, aged 33, in Ballyronan.
The officer in charge of the investigation, Detective Superintendent Raymond Murray, said: “Our determination to pursue every possible line of inquiry remains undiminished.
“The investigation is progressing and police have been encouraged by the support and assistance which has been forthcoming from across the community.
“During this search stage, we would ask for people’s continued patience and co-operation as we work to complete our inquiries to maximum effect, as expeditiously as possible and with the minimum amount of disruption to community life.”