BBC Online : Islamic State (IS) is a threat to the “streets of Britain” and the UK has a “duty” to confront it, David Cameron has said as MPs debate air strikes. The prime minister said it was in the UK’s interest to join in bombings against IS in Iraq and there was also a strong case for action in Syria. Parliament is due to vote on UK involvement in Iraq at about 17:00 BST. Downing Street has said a small number of troops could be sent to Iraq within hours if the Commons backs action. However, the prime minister’s official spokesman emphasised the troops would not be in a combat role but would be used to guide air strikes, in a humanitarian role and, possibly, to train Iraqi and Kurdish peshmerga forces, although this may take place in neighbouring countries. Syria next? The government is expected to win the vote comfortably, with the Conservatives, Liberal Democrats and Labour all supporting the action after it was requested by the Iraqi government. Mr Cameron told MPs there was a “strong case” for the UK to do more in Syria, where America and Arab allies are engaged in aerial bombardment of IS positions. The PM said he did not believe there was any “legal barrier” to military action there – but he acknowledged there was no consensus for such a move among MPs. Downing Street said there would be no action in Syria without a Commons vote unless there is an urgent humanitarian need to do so. In other developments: The Pentagon said four IS tanks had been destroyed during the latest raids in SyriaLabour leader Ed Miliband said IS “cannot and should not be negotiated with”.The widow and daughter of murdered British aid worker David Haines back RAF air strikesSpeaking in the House of Lords, the Archbishop of Canterbury, Justin Welby, supported action but called for “an ideological and religious” solution rather than a military one.Denmark is to contribute seven planes to the international coalition against ISThe number of Europeans joining Islamist fighters in Syria and Iraq has risen to more than 3,000, the EU’s anti-terrorism chief says IS has seized large parts of Iraq and Syria in recent months. The group, also known as Isis or Isil, has used tactics that have included beheadings of soldiers, Western journalists and aid workers. Making the case for British action, Mr Cameron said the killing of a British hostage illustrated that the challenge was not “on the far side of the world” and the “brutal, terrorist organisation” was a “clear and proven” threat to UK lives. “This is not the stuff of fantasy. It is happening in front of us and we need to face up to it,” he said.