LONDON (AFP) - Britain unveiled emergency laws on Tuesday (Feb 11) to stop convicted terrorists from being automatically released part-way through their prison sentences, following two attacks in London.

The government hopes the bill will swiftly pass through parliament and become law by the end of the month.

"No dangerous terrorist should be released automatically only to go on to kill and maim innocent people on our streets. Enough is enough," said Justice Secretary Robert Buckland.

Prisoners are currently released on licence around half-way through their sentences.

Under the proposed new law, terror convicts will only be considered for release after serving two-thirds of their sentence, and then only after consideration by a parole board.

The change will affect around 50 prisoners currently behind bars.

Usman Khan, 28, stabbed two people to death in November in a knife attack near London Bridge while attending a prisoner rehabilitation conference.

He was wearing a fake suicide vest and was quickly shot dead by police.

Sudesh Amman, 20, stabbed two people on Feb 3 in Streatham, south London, within weeks of being released early from prison.

He was also wearing a fake suicide vest and was killed by armed officers.

Amman was freed from prison after serving part of his sentence for 16 Islamist-related terror offences - namely the possession and distribution of terrorist documents.

Prime Minister Boris Johnson questioned why Amman had been released automatically with no involvement from the parole board and raised concerns about the effectiveness of de-radicalisation programmes in and out of jail.

"We are stepping-up de-radicalisation measures in our prisons, introducing a 14-year minimum for the worst terrorist offenders, and giving more money to the police to deal with these horrific crimes," said Buckland.

"In addition to the bill, the government will ensure that when a terrorist offender is released they will be subject to robust safeguards, which could include notification requirements, restrictions on travel and communications, and imposed curfews."