Three more men were arrested in the city on Wednesday as British authorities continued to conduct “extensive” searches while investigating the “network” behind the attack carried out by British-born Salman Abedi.
“It is very clear that it is a network we are investigating,” Manchester police said.
Abedi killed 22 persons and injured 64 when he blew himself up outside an Ariana Grande concert. He was born in Manchester to parents of Libyan descent and had ties to Al Qaeda, BBC reported.
Interior minister Amber Rudd told the press earlier in the day that it was likely that Abedi was not working alone and that he was up to a point known to British secret services.
Abedi’s 23-year-old brother was arrested on Tuesday in a raid. Reports said that Abedi returned from a visit to Libya just days before carrying out the Manchester attack and may have travelled to terrorist strongholds in Syria.
The country’s terror threat level was raised to its highest “critical” level, meaning more attacks may be imminent. Under the order, armed military personnel replaced police guarding “key sites”. Nearly 1,000 soldiers were deployed on Britain’s streets to support police.
Abedi had a sister and two brothers. Abedi’s mother and father were now believed to be back in Libya. His family lived at more than one address in the city, including a property at Elsmore Road in the Fallowfield area that was raided by police.
Abedi was identified by a bank card found in his pocket at the scene of the explosion.
The 22-year-old was known to security services as an associate of IS recruiter Raphael Hostey, also from Manchester, who was killed in a drone strike in Syria last year.
Amid ongoing investigations and raids, the Palace of Westminster was closed to the public following police advice, and will not re-open until further notice, a statement on its website said.
The Changing the Guard ceremony at Buckingham Palace was cancelled to allow for the redeployment of police officers, the Ministry of Defence said.
German chancellor Angela Merkel signed a book of condolence for the victims of the Manchester attack at the British Embassy in Berlin.
A Polish couple from York was among 12 victims identified and the injured in the attack were being treated at eight Greater Manchester hospitals. Of those, 20 were in a critical condition.
The Manchester attack came two months after the Westminster attack.