Manchester bombing: Polish couple who went missing in attack confirmed dead

Their children are safe

Floral tributes left by Manchester Town Hall after a suicide bomber killed 22 people leaving a pop concert at the Manchester Arena on Monday night (Ben Birchall/PA)

A Polish couple died in the suicide attack in the Manchester terror attack, Poland's Foreign Minister has said.

Angelika and Marcin Klis died on Monday evening, when a suicide bomber detonated a suitcase bomb as crowds were leaving an Ariana Grande gig.

Their daughter been publicly searching for them since the explosion.

A selfie taken by Angelika and Marcin Klis shortly before the attack (Facebook/Alex Klis)

"The parents came after the concert to collect their daughters and unfortunately we have information that they are dead. The children are safe," Witold Waszczykowski told private radio RMF FM.

Another Polish father was injured in the blast and underwent surgery, he added.

Britain is on critical terror alert with military troops set to bolster police forces amid fears Manchester Arena attacker Salman Abedi did not act alone.

Prime Minister Theresa May has raised the threat level to the highest possible rating, meaning another atrocity is expected imminently.

She said a "wider group of individuals" could have been involved in the Manchester Arena blast rather than just suicide bomber Abedi.

In a sign of the increased threat, the military could be deployed to support armed police officers, Ms May added during a live televised statement from Downing Street.

Monday night's attack at a concert by US pop star Ariana Grande left 22 people dead, including an eight-year-old girl, and dozens injured.

Counter-terrorism agencies have mounted a massive inquiry into the outrage - the worst terrorist attack since 52 innocent people were killed in the 7 July bombings in London in 2005.