The death toll from the London Bridge terror attack has risen to eight after the body of a victim was found in the River Thames.

British police searching for 45-year-old Frenchman Xavier Thomas, who had been missing since Saturday’s attack, said Thursday morning (AEST) they found a body in the river downstream from London Bridge.

It is believed Mr Thomas, whose girlfriend was seriously injured in the attack, was knocked from the bridge when three terrorists ploughed into pedestrians before jumping from a van and attacking people with knives.

Police have now named all the victims of the attack, including Australians Kirsty Boden, 28, and 21-year-old Sara Zelenak.

The other victims are Canadian national Chrissy Archibald, 30, James McMullan from London, 32, French nationals Alexandre Pigeard, 27, and Sebastien Belanger, 36, and Spaniard Ignacio Echeverria, 39.

Kirsty Boden (L) and Sara Zelenak (R) are confirmed as being among the eight victims.

Ms Zelenak’s mother Julie Wallace, who flew to London in the hope of finding her missing daughter, broke the tragic news of Sara’s death on Facebook on Wednesday afternoon.

“Sara Zelenak is confirmed dead. They found her body and DNA tests have confirmed,” the post read.

“Thank you for all the overwhelming love and support from everyone.”

Ms Zelenak was separated from her friend on London Bridge when the violence began and was last seen fleeing the attack.

Late on Tuesday, it was confirmed that South Australian nurse Kirsty Boden was also killed.

The Boden family said Kirsty, 28, was running to help victims of the stabbing and van attack when she was fatally injured.

“As she ran towards danger, in an effort to help people on the bridge, Kirsty sadly lost her life,” they said.

The discovery of Mr Thomas comes as UK authorities face new questions over how one of the London Bridge attackers was allowed into Britain despite being on a security watch list.

Youssef Zaghba had been flagged to British intelligence services after telling Italian police “I’m going to be a terrorist” when he was reportedly stopped trying to travel to Syria.

Italian prosecutor Giuseppe Amato said there was not enough evidence to arrest or charge the 22-year-old when he was caught at Bologna airport last year.

He said Zaghba was always tracked by Italian intelligence officers while in the country and that UK authorities were informed.

“We did everything we could have done, but there weren’t elements of proof that he was a terrorist,” he added.

The youngest of the attackers, an Italian national of Moroccan descent, he was allowed to enter the UK and had been living in east London.

Counter-terror agencies were already under intense scrutiny after it was revealed Khuram Shazad Butt, 27, and Rachid Redouane, 30, were also known to security services.

All three attackers were killed by police at the scene of the atack.

– With agencies