The ICRC said the team had gone to Idlib on Thursday to assess the medical situation in the province and to deliver medical supplies to Sarmin and Idlib city.
The convoy was clearly marked with the ICRC emblem when stopped near Sareqeb on the way back to Damascus, it added.
Spokesman Ewan Watson told Reuters the humanitarian agency has had no contact with the unidentified gunmen
Syrian state media reported the incident earlier in the day, saying the gunmen had kidnapped the Red Cross workers after opening fire on their vehicles on Sunday.
Mr Watson was not able to confirm that shots had been fired, but said the team's vehicles were also missing.
Kidnappings have become increasingly common in northern Syria, where rebels have captured swathes of territory but government forces have clung on to many urban centres and fighting continues daily.
The ICRC and Syrian Arab Red Crescent are the main aid groups deployed in Syria's civil war, distributing their own supplies and most of those sent by United Nations agencies.
They have to negotiate the passage of aid convoys with a growing number of groups within the fractured opposition, ICRC officials say.
