British police said they would deploy more armed officers than usual on the streets of London for New Year's Eve, as the terror threat level remains at "severe" meaning an attack is "highly likely".

Some 3,000 police officers will be deployed in central London on Friday, where there will be the traditional fireworks display along the River Thames near the Houses of Parliament, the police said.

The Daily Telegraph said all the armed officers in London - around 2,000 people - would be deployed in "an unprecedented anti-terror security operation".

Metropolitan Police spokeswoman Jo Edwards said: "The public can expect to see additional police officers in central London, which includes an increased number of firearms officers.

"Our plans are purely precautionary and not as a result of any specific intelligence," she said.

For the second year running access to central London to view the fireworks is by ticket only and all 113,000 have been sold out.

Roads in central London will start being closed off from 1400 GMT.

Westminster, Soho, Piccadillly and the area around Buckingham Palace will be entirely car-free between 2000 GMT and 0600 GMT.

Public transport will be free and run until 0430 GMT.

The terror threat level in Britain was last raised in August 2014 to four out of five grades.

Since August 2014 the threat level in Britain has been at four out of a total of five.

Prime Minister David Cameron earlier said that seven terror plots have been foiled in Britain in the past year.