Three more men have been arrested as police continue to investigate whether Manchester Arena bomber Salman Abedi acted alone.

Police arrested the three in the city on Wednesday. Abedi's 23-year-old brother was arrested on Tuesday, reports the BBC.

Abedi killed 22 and injured 64 when he blew himself up outside an Ariana Grande concert on Monday night.

The UK terror threat level is now up to its highest level of “critical”, meaning more attacks may be imminent.

It means military personnel are being deployed to protect key sites.

The Palace of Westminster has been closed to the public following police advice, and will not re-open until further notice, a statement on its website said.

And the Changing the Guard ceremony at Buckingham Palace has been cancelled on Wednesday to allow for the redeployment of police officers, the Ministry of Defence said.

Home Secretary Amber Rudd said: “[Monday's attack] was more sophisticated than some of the attacks we've seen before, and it seems likely - possible - that he wasn't doing this on his own.”

BDST: 1845 HRS, MAY 23, 2017
AP