Qatar is working to help free four Americans held hostage in Syria by various armed groups, a Gulf source familiar with the matter said on Monday, a day after the country's diplomacy helped free a journalist held since 2012.

The source declined to name the four or provide details, and Reuters could not independently verify the assertion, but his account was broadly supported by other sources.

The reported initiative by Qatar coincides with an effort by the state to rebut accusations by some of its Arab neighbours and Western politicians that it supports the most anti-Western militant armed groups in Iraq and Syria.

The country, which does back some rebel factions fighting to oust Syrian President Bashar Al-Assad, has mediated the release of foreign and Syrian captives on several occasions in the course of Syria's three-year- old civil war.

Its latest foray into hostage diplomacy brought Sunday's release of Peter Theo Curtis, an American held for nearly two years by Al-Nusra Front, an affiliate of Al Qaeda.

"Four other Americans who have gone missing in Syria have now been located, and Qatar is working to free them," the Gulf source told Reuters on condition of anonymity. He said the hostages were being held by "various groups" but declined to give details.

Qatar's foreign ministry declined to comment.

A Doha-based source close to the Qatari government said without elaborating that Washington was working with Qatar to try to free a number of US hostages in Syria.

A rebel commander in Syria reached by Skype from Beirut told Reuters that Qatar was continuously trying to secure the release of captives of all nationalities.

BEHEADING

"Qatar has good connection here on the ground with various groups," he said. "Freeing hostages is their
priority, and whenever there is a chance, they help. They use these connections to release hostages. Right now they are working on several issues regarding hostages."

A Syrian opposition official in Doha said Qatar was trying to secure the release of a number of hostages
across Syria, but did not say how many.

"Qatar has very good connections with brigades inside Syria. That's why their attempts have been successful, and more efforts are being made to free a number of hostages across the country," said the official, who asked not to be identified.

In Washington, a US State Department spokesperson said the US government over the past two years had reached out to over two dozen countries asking for help from anyone who could help secure the release of American citizens held in Syria.

News of Curtis's release emerged just days after Islamic State, a splinter Al Qaeda group that operates in Syria and Iraq, posted a video on the Internet showing one of its fighters beheading American journalist James

Foley, who was kidnapped in Syria in 2012.

Qatar's role in securing Curtis's freedom may help repair a reputation dented by allegations from some of its Arab and Western critics that Doha supported Islamic State and some other radical groups in Iraq and Syria.

Qatar denies it backs militant groups with Al Qaeda ties, but it has been at odds for months with some fellow Gulf states over its longstanding support for the Muslim Brotherhood, a transnational Islamist group, and charges by Saudi Arabia and the UAE that Doha interferes in their internal affairs.

Under a policy of international self-promotion, Qatar has for years also played peace broker in disputes from Somalia to Lebanon, and has irritated conservative neighbours by supporting Arab Spring revolts and bankrolling Islamist influence.

Qatar this week argued its aims in the region were peaceful and humanitarian, issuing a statement condemning what it called Foley's "barbaric" murder. - Reuters