"Good news! We confirm that the Syrian Red Crescent volunteer and 3 out of 6 @ICRC colleagues have been released safe & sound. #Syria," said Robert Mardini, ICRC head of operations for the Middle East, on his Twitter page.
"We are still doing our utmost to have our 3 other colleagues back safe & sound," Yves Daccord, director general of the international organization posted on Twitter.
The workers were abducted Sunday in Idlib province. It is not clear who kidnapped them.
They were freed near the Turkish border, the BBC reported.
Meanwhile, the head of the international chemical weapons watchdog said Monday inspectors faced problems accessing some of the chemical weapons sites because of fighting.
Ahmet Uzumcu, director general of Nobel Peace Prize laureate Organization for the Prohibition of Chemical Weapons, told the BBC President Bashar Assad's government had been cooperating with inspectors had reached five of 20 chemical weapons production sites.
As inspectors resumed their task, officials said at least 22 people were killed Monday when a car bomb detonated in the main square in Darkoush, a rebel-held town in Idlib province near the Turkish border, al-Jazeera reported.
The Syrian Observatory for Human Rights said the toll was expected to rise because many people sustained serious injuries. The number of injured was not reported.
Uzumcu said inspectors experienced "access problems" at some sites because of the fighting that has ravaged the country for more than two years, he said.
Some roads "change hands from one day to another, which is why we appeal to all sides in Syria to support this mission, to be cooperative and not render this mission more difficult," Uzumcu said. "It's already challenging."
Inspectors began arriving Oct. 1 under an agreement brokered by the United States and Russia for Syria to destroy its chemical weapons capability after an Aug. 21 gas attack in a suburb of Damascus. Assad has denied accusations from western countries that Syrian government forces were responsible for the attack, which killed hundreds of people.
Uzumcu said inspectors were so close to the fighting that once mortar shells exploded "next to the hotel where our team is staying, and there are exchanges for fire not far from where they go."
The OPCW and the United Nations have a team of about 60 experts and support staff in Syria, the BBC said.
He told the BBC he had called for truces because "in the previous, U.N.-led mission to investigate allegations of use [of chemical weapons] there were temporary cease-fires of four or five hours which helped this mission."
It is the first time the OPCW has worked in a war zone since it was established in 1997, the BBC said
The inspectors face a rigid deadline set by the United Nations to complete their work by mid-2014. Under terms of the resolution, Syria's chemical weapons production equipment must be destroyed by Nov. 1 and stockpiles disposed of by mid-2014.
On Monday, Syria became the 190th member of the Organization for the Prohibition of Chemical Weapons by formally acceding to the 1997 Chemical Weapons Convention.
Uzumcu said the Nobel award announced Friday was "a very big boost of morale" for the inspectors.
"They are working in very challenging circumstances in the field," he said. "In awarding the prize, they said it was about recognizing the work of the past 16 years, but also the work that lies ahead, in Syria."