Gunmen released have three Red Cross workers and one Red Crescent volunteer after holding them overnight, but three Red Cross staffers were still in captivity.

International Committee of the Red Cross (ICRC) Middle East operations chief Robert Mardini said the four had been released "safe and sound."

Unknown fighters had abducted six Red Cross workers and the Red Crescent volunteer after stopping their convoy early on Sunday in north-western Syria.

Red Cross spokesman Simon Schorno said the kidnappers snatched the aid workers near Saraqeb in Idlib province as they were returning to Damascus.

He said it was not clear who was behind the attack.

Syria's state news agency said the gunmen shot at the ICRC vehicles before seizing the workers.

Mr Schorno said the team of seven had been in the field since October 10 to assess the situation and to look at how to provide medical aid.

He said the part of northern Syria where they were seized "by definition is a difficult area to go in," and the team was travelling with armed guards.

Much of Idlib province has fallen into the hands of rebels over the past year and kidnappings have become rife, particularly of aid workers and foreign journalists.

Press freedom group Reporters without Borders says Syria is "the most dangerous country in the world" for journalists, with 25 reporters killed and at least 33 imprisoned since the anti-government uprising began in March 2011.

The conflict has also taken a toll on aid workers.

The ICRC said in August that 22 Syrian Red Crescent volunteers have been killed in the country since the conflict began.

Some were deliberately targeted while others died in crossfire.

Outside Damascus several thousand civilians, some carried on stretchers, fled the rebel-held suburb of Moadamiyeh following a temporary ceasefire in the area.

It was not clear who brokered the weekend halt in fighting between rebels and government forces, but it marked a rare case of co-ordination between the opposing sides in Syria's civil war.