DHAKA: Britain’s security services are monitoring thousands of terrorism suspects in London and are involved in operations on a daily basis.

The capital’s mayor Boris Johnson said in an interview published on Saturday.

‘In London we’re very, very vigilant and very, very concerned,’ London mayor Johnson told the Daily Telegraph newspaper, reports The Straits Times.

In August, Britain raised its international threat level to the second-highest classification of ‘severe’, meaning an attack was considered highly likely, with prime minister David Cameron warning that militants from the Islamic State (IS) posed the country’s greatest ever security risk.

About 500 Britons are believed to have joined the fighting in the region and the authorities have long argued that radicalised, battle-hardened veterans would pose a grave threat on their return.

BDST: 1806 HRS, OCT 11, 2014