Witness accounts of the terror attacks in London are flooding in as people recount seeing victims bleeding in the streets and begging for help.

A Londoner has told the BBC he saw people being stabbed and chased down by the attackers, throwing objects at them in an attempt to save people.

“I ran up and they were stabbing this girl, three of them, I was defenceless, I couldn’t do nothing,” he said.

“They were stabbing everyone.”

The man said he followed the attackers to Borough Markets, where he said they entered a number of pubs.

“They were running in all the pubs, all the bars, I can’t remember all of them, but they were running in, they were stabbing everyone.

“I was throwing bottles at them, pint glasses, stools chairs, I tried to help as many people as a I could but at the end of the day I was defenceless.”

The man said he saw one girl stabbed 10 to 15 times, but he was unable to help her.

“She was going ‘help me, help me’ but I could not do nothing,”

The man said he tried to throw things at the suspects to get them away from the girl but had no luck.

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Another man who was at the Mudlark pub, which is located below the famous bridge, said a woman with a slash wound across her throat came into the venue seeking help.

“At around 10pm BST (7am Sunday AEST) an injured woman came into the pub seeking assistance,” Alex Shellum told the BBC.

"She was bleeding heavily from the neck - it appeared that her throat had been cut. People sought to stem the bleeding.”

Mr Shellum said the pub was immediately closed and he moved into the street, where police were swarming the area.

Outside the pub, emergency services were performing CPR on a further individual,” he said.

Mr Shellum said he was shuffled into a restaurant by police and instructed to hide in the kitchen while they swept the area.

Kumi de Costa told BBC she was in a taxi with two friends when they “got stuck right in the middle of the shooting” at Borough Markets and saw victims on the ground around them.

“There were loads of shots being fired,” she said.

“About 50 police were pointing guns at us - the cab driver had the laser pointed right at them, our hands were up, we were trying to get out so they shooed us away.

“A man was coming out of the restaurant, he had a napkin on his neck with blood pouring out, there was another man lying on the floor. I don’t know if he was in the recovery position or dead.”

A Londoner named James told 9NEWS he saw “two armed mark police” shooting and shouting at someone to “get back”.

“Three shots (were) let off,” he said.

British resident Ollie Andrews, who is holidaying in London at the moment, said he heard screams and watched a bloodied victim be loaded into an ambulance.

“We were in a pub right outside the attack, it was right next to the underground station,” he said.

“People screaming left right and centre.

“We didn’t know what to do until police came in the front door and busted us all out,” he said.

Mr Andrews said he was told to “make a run for it”.

“We saw one of the victims covered in blood being stretched out to go into the ambulance, he wasn’t in a good shape.”

Kaine Pieri told 9NEWS he was coming out of London Bridge station when he saw a number of police cars pull up and was told to run.

“There was a white van that police with armed guns, opened the back, and started rummaging.

“One man ran away in a white t-shirt and a policeman was running after him.

“They were screaming at us to get away.

“We saw a crowd of people walking past us, tears in their eyes, looking really shocked, and I heard someone talking to someone about seeing someone passing away.”