By Andrew Osborn
LONDON (Reuters) - Law enforcement authorities in Britain are increasingly worried about the risk of a "lone wolf"-style militant attack and have foiled four or five plots this year, London's top police officer said on Sunday.
The assertion, by Bernard Hogan-Howe, the commissioner of London's Metropolitan Police, comes on the eve of a terrorism awareness campaign and as the government prepares to introduce a law that would make it easier for the police to identify who is using a computer or a mobile phone at any given time.
Britain has been considered a target for Islamist militants since the Sept. 11, 2001, al Qaeda attacks on the United States, and 52 people were killed when four young Britons carried out suicide bombings in London in 2005.
Britain raised its terrorism alert to the second-highest level in August, saying militants in Syria and Iraq posed the biggest threat to its security. That meant an attack was deemed highly likely for the first time since mid-2011.
When asked whether lone wolf attacks were now the biggest worry after the 2013 murder of Lee Rigby, a British soldier, by two machete-wielding Muslim converts, Hogan-Howe suggested the risk of further such attacks was increasing.
"We've certainly seen over the last few months a growing concern about exactly the type of attack you just described," he said on BBC TV's Andrew Marr Show.
"It doesn't take an awful lot of organising, it doesn't take too many people to conspire together, there's no great complexity to it, so what that means is that we have a very short time to interdict, to actually intervene, and make sure that these people don't get away with it."
The authorities usually foiled one terrorist plot a year, he said. But in 2014 they had thwarted "four or five" as the frequency and seriousness of such plots had escalated.
Police estimate over 500 Britons have travelled to Syria and Iraq to fight, though Khalid Mahmood, a Labour lawmaker, told a Sunday newspaper he thought the real number was closer to 2,000, some of whom had already returned to Britain.
Hogan-Howe said such returnees would be "militarised" with contacts and knowledge of new tactics they might want to use.
Police will this week explain to the public how to remain vigilant as part of a campaign to prevent any attacks.
(Editing by Stephen Powell)