LONDON - Britain faces the threat of a Sydney-style ‘lone wolf’ attack at any moment, Prime Minister David Cameron said on Tuesday, after a 16-hour siege at a cafe in the Australian city in which two captives were killed.

Britain raised it terrorism alert to the second-highest level in August and last month said it was facing the biggest terrorism threat in its history because of radicalised Britons returning from fighting in Syria and Iraq. ‘The threat we face definitely includes those sorts of self-starting, sometimes quite random attacks that could happen at any moment in Britain,’ Cameron told a committee of lawmakers when asked how close Britain was to a Sydney-style attack. ‘People who are self-radicalised on the Internet who then suddenly do appalling things, that is much more difficult to prevent.’ Moreover, Police stormed the Lindt coffee shop in the city’s business district on Tuesday, freeing terrified hostages and ending a 16-hour siege in which two captives and the gunman were killed.

Advocates are calling for an intensification of efforts to trace stolen weapons and ensure compliance with federal laws prohibiting semi-automatic rifles and some shotguns.

Police have not said how the hostage-taker, Man Haron Monis, who had a criminal record, obtained the weapon he used. Australia in 1996 enacted what detractors at the time called draconian restrictions on gun ownership under The Agreement on Firearms act in response to a mass shooting that left 35 people dead in Port Arthur in the island state of Tasmania.

A mandatory national buyback of outlawed guns was included in the legislation championed by then Prime Minister John Howard and resulted in more than 700,000 firearms being turned in. The A$500 million ($411 million) cost of the buyback was met by a special one-off tax imposed on all Australians. ‘The gun laws we were meant to have after the Port Arthur massacre are now watered down quite significantly,’ said Samantha Lee, chairwoman of Gun Control Australia (CGA).

‘In the wake of the siege, GCA is calling on review of gun laws and in particular an audit of state and territory compliance with the 1996 Agreement on Firearms, storage requirements and gun dealer compliance with firearm laws,’ Lee said. A campaigner opposed to stricter gun laws accused the GCA of using the siege in Sydney to score points with legislators. ‘They are unashamedly looking to exploit this latest tragedy for their own purposes,’ said Robert Borsak, a state parliamentarian and head of the Shooters and Fishers Party.

The party was formed in 1992 to oppose laws preventing citizens from owning firearms for self-defence. Borsak is leading a call for the repeal of a bill requiring gun owners to leave their name and address at the shop each time they buy ammunition. Borsak said the bill puts firearm owners and their families at risk by providing criminals with a potential ‘shopping list’ of targets. Nearly 600 guns were stolen in the past year in New South Wales state alone, 80 percent from homes, according to the state’s Bureau of Crime Statistics. The most common weapons to be stolen were rifles, followed by shotguns and handguns, the figures show.