The men - two arrested in Staffordshire, the other three in the capital - were held after two devices exploded in North London late on Friday night. The bombs were planted about two miles apart at Staples Corner on the North Circular Road and West End Lane, West Hampstead.
The latest attack is the IRA's third in North London in a week. Last Saturday three bombs exploded in Finchley Road, and on Monday another five detonated in Highgate.
Scotland Yard said a 'particularly obscure and unclear' warning was telephoned to a local mini-cab firm at 11.15pm on Friday - about 20 minutes before the explosions began - giving a general location where the devices had been planted.'
The first device caused a small explosion outside a warehouse, while the second, thought to have been placed beneath a car parked outside a dry cleaner's, blew out windows at nearby flats and shops. No one was injured in either incident but several families were evacuated for five hours while the area was searched.
In April 1992, the IRA exploded a 100lb bomb in a van at Staples Corner.