Vienna: Swiss President and OSCE chief Didier Burkhalter slammed the detention of observers in eastern Ukraine Wednesday as "acts of sabotage," as a team of monitors remained missing.
In a statement, Burkhalter said the detention of a observers from the OSCE`s special monitoring mission in Ukraine "cannot be tolerated" and were "acts of sabotage of international efforts to assist Ukraine in overcoming the crisis."
He called for their "immediate and unconditional release."
The Vienna-based Organisation for Security and Co-operation in Europe said Tuesday it had lost contact with a team of four observers, monitoring the situation in restive eastern Ukraine.
The team -- a Dane, an Estonian, a Turk and a Swiss national -- were apparently detained at a checkpoint shortly before contact was lost.
Ukraine`s foreign ministry has meanwhile accused rebels of holding them.
On Wednesday, an OSCE spokesperson confirmed there still hadn`t been any contact with them.
A second group of 11 observers was detained in the same region of Donetsk on Wednesday but the OSCE later said it had managed to re-establish contact with them.
"We can`t confirm their status until we have them back with the rest of the mission, safe and sound," an OSCE spokesperson said in Vienna.