Six people died and at least 30 were injured as a vehicle barrelled into pedestrians on London Bridge and three attackers embarked on a stabbing rampage at nearby Borough Market in the heart of the British capital on Saturday night, media reports said.

The incident was reported at 10:08 pm local time, NBC News reported, adding that within eight minutes, all of the suspects had been fatally shot by officers, citing authorities.

"At this stage, we believe that six people have died in addition to the three attackers shot dead by police. And at least 20 casualties have been taken to six hospitals across London," Assistant Commissioner of Metropolitan Police Mark Rowley was quoted as saying by Russian news agency Tass.

"The vehicle continued to drive from London Bridge to Borough Market. The suspects then left the vehicle and a number of people were stabbed," he added.

"The suspects had been confronted and shot by the police within eight minutes of the first call," Rowley said.

"The suspects were wearing what looked like explosive vests but these were later established to be hoaxes," he added.