Britain should play a leading role in international efforts to step up sanctions against Syria, Prime Minister David Cameron said on Wednesday, calling Syrian President Bashar al-Assad a wretched tyrant.

Cameron also said there was growing evidence that Iran was helping to prop up the Syrian leader.

Britain needs to lead the way in making sure we tighten the sanctions, the travel bans, the asset freezes, on Syria, Cameron told parliament.

In terms of who is actually helping the Syrian government to oppress their people, there is now growing evidence that Iran is providing a huge amount of support, he added.

People should also know that Hezbollah is also an organisation that is standing up and supporting this wretched tyrant who is killing so many of his own people.

Further European Union sanctions are expected to be discussed at a meeting of EU foreign ministers next Monday.

(Reporting by Keith Weir; Editing by Adrian Croft)