International Committee of the Red Cross (ICRC) spokesman Simon Schorno said the three Red Cross staff and the Syrian Red Crescent volunteer "seem in good health" after their release.
Speaking in Damascus, Mr Schorno said, "We haven't spoken to them yet but they seem to be in good health and safe".
The ICRC is networking with a number of people in northeastern Syria to ensure the three Red Cross workers still being held are released "unconditionally and very rapidly".
The International Committee of the Red Cross (ICRC) said it remains "committed to serving the Syrian people" after six staff members and a Syrian Red Crescent volunteer were kidnapped.
The ICRC's head of operations for the Middle East, Robert Mardini, has confirmed three of those kidnapped have since been released.
The International Committee of the Red Cross has confirmed that three of the six members of staff kidnapped in Syria have been released along with a Syrian Red Crescent Volunteer.
They are are "safe and sound" in Syria, Reuters reports.
The International Committee of the Red Cross (ICRC) said its teams in Syria and Geneva "are doing their utmost" to find the seven people kidnapped and bring them back "safe and sound".
The ICRC's head of operations for the Middle East, Robert Mardini, also said the group's operations would continue in Syria:
The head of the International Committee of the Red Cross (ICRC) said the group's thoughts "are with our colleagues and their families" following the kidnapping of seven Red Cross workers in northern Syria.
Director general Yves Daccord wrote on Twitter:
The International Committee of the Red Cross has called for the "immediate and unconditional release" of the seven workers kidnapped in northern Syria on Sunday.
Armed men abducted six ICRC staff members and one Syrian Arab Red Crescent volunteer near Sareqeb, in north-western Syria as they travelled back to Damascus at around 11:30am (08:30 GMT) this morning.
In a statement, the humanitarian group said: "We call for the immediate and unconditional release of the seven colleagues abducted this morning.
"Both the ICRC and the SARC work tirelessly to provide impartial humanitarian assistance for those most in need across Syria on both sides of the front lines, and incidents such as these potentially undermine our capacity to assist those who need us most."
A spokesman for the International Committee of the Red Cross in Damascus has confirmed that seven of the group's workers have been kidnapped in northern Syria.
Simon Schorno said gunmen abducted the six ICRC workers and one Syrian Red Crescent volunteer near the town of Saraqeb in Idlib province at around 11:30am (08:30 GMT) on Sunday.
Mr Schorno declined to comment on the possible nationalities of the kidnapped employees.
The International Committee of the Red Cross said seven of its workers have been kidnapped in northern Syria, the Associated Press reports.
The International Committee of the Red Cross has confirmed reports that an incident took place at its office in Jalalabad, Afghanistan.
The impact of possible chemical weapons in Syria on aid efforts would be difficult to anticipate, the International Red Cross said at a conference in the Switzerland headquarters.
Officials said it would attempt to continue humanitarian operations in Syria in the event of chemical weapons being used. Syria have denied that it would use chemical weapons. President Peter Maurer told reporters: