Police arrested a second man on Friday in connection with an explosion in the toilets of a busy restaurant in southern England a day earlier.

Nicky Reilly, 22, an Islamic convert with a history of mental illness, was arrested on Thursday and taken to hospital after he detonated a bomb in a branch of the family-oriented Giraffe restaurant chain in the centre of Exeter.

Police said armed officers arrested the second man on Friday in Plymouth and a third was being questioned.

"At 3.30 p.m. today Devon and Cornwall police arrested one man in connection with yesterday's incident in Exeter," a police spokesman said. "The man arrested is now in custody as part of the ongoing investigation."

Although limited in scope, the attempted attack was a reminder of earlier bombings in Britain, such as the strikes in July 2005 when four Islamist suicide bombers killed 52 commuters on London's transport system with homemade bombs.

Reilly was the only person injured in the explosion. Police later discovered and disarmed two other devices nearby.

Local media quoted police sources as saying Reilly's device was a "viable" bomb made of sodium hydroxide, kerosene, aluminium and nails. They also said he received a text message of encouragement on his mobile phone before the blast.

Police spokesmen could not confirm the reports.

Police said Reilly suffered cuts to his eyes and burns to his face, but his injuries were not life threatening.

Security services say they have foiled numerous bomb plots in Britain since the September 11, 2001 attacks on New York and Washington.