Three out of six kidnapped Red Cross members and a Red Crescent volunteer have been “released safe and sound” in Syria, the ICRC says.
The head of ICRC’s operations for the Middle East, Robert Mardini, broke the news via a tweet.
The organisation says it is awaiting information on the remaining three.
The workers were abducted on Sunday near Saraqeb, in Idlib province, where they were delivering aid and assessing health facilities.
It is not clear who carried out the kidnapping.
Syrian state television blamed what it called armed terrorists – a term it frequently uses to describe anti-government rebels.
The ICRC said the aid workers were released in Idlib province, near the Turkish border.
The agency has not released details of their nationalities or the circumstances under which they were freed.
“Of course this type of incident is terrible because it is disruptive and puts in jeopardy our operations in Syria,” Mr Mardini told Reuters earlier.
But he said the ICRC remained committed to its relief operations in Syria.