The Metropolitan Police has not given details about the locations or types of properties, or how many of the men are linked to the area.
The men are being held on suspicion of the commission, preparation or instigation of acts of terrorism.
There have also been searches in London as part of the operation - thought to be linked to Syria-related terrorism.
Two men, aged 33 and 43, were held as they tried to leave the UK at Dover port on Sunday while two other men, aged 24 and 40, were arrested in east London early on Monday.
A 28-year-old man was held in Dover later that same day.
Police have been given more time to question the men who are are being held in custody.
The terror threat level in the UK was raised from substantial to severe in August.
Fears of a terrorist attack on the UK have been heightened in the wake of the rise of Islamic State (IS), the extremist group that has taken over large swathes of Iraq and Syria.
Police are continuing to search two addresses in north Wales following the arrest of five terror suspects.