Dubai: British Prime Minister David Cameron said yesterday he planned to introduce new legislation to make it harder for Britons to travel to Syria and Iraq to fight alongside Islamist extremists as the country raised its international terrorism threat level to “severe”, its second highest level.

Cameron said he would detail his plans in parliament on Monday to confiscate passports. “I will be making a statement in the House of Commons on Monday. This will include further steps to stop people travelling, with new legislation that will make it easier to/stake people’s passports away,” Cameron said.

Earlier, home secretary Theresa May said that terrorist groups in Syria and Iraq were planning attacks against the west and it means that an attack is “highly likely”, though there is no evidence to suggest an attack is imminent.

The home secretary said some of the plots were likely to involve foreign fighters who had travelled to the Middle East from Britain and Europe to take part in the conflicts there.

Some 500 Britons are thought to have travelled to Syria and Iraq to fight with militant groups such as Islamic State of Iraq and the Levant (Isil), which have seized a huge swath of territory along the Euphrates and Tigris rivers from Aleppo in Syria to the outskirts of Baghdad in Iraq.

The decision to raise the threat level to one notch below “critical” was made by the Joint Terrorism Analysis Centre, which acts independently of ministers.