Tbilisi/Moscow - EU observers started their mission Wednesday to monitor the Russo-Georgian ceasefire agreement one and half months after conflict flared between the two countries over Georgia's breakaway regions of South Ossetia and Abkhazia.

Russian troops still in Georgia prevented the observers from entering the security zone they set up around South Ossetia.

"It is not a categorical ban on the EU mission; it's just that the details of the monitoring mission have not been cleared up yet," a Russian military spokesman told Interfax news agency.

A decision on allowing the EU observers into the buffer zone would be taken later, he said.

The 350 EU observers, most of whom are police officers, are in the region to monitor the ceasefire and the withdrawal of Russian troops from the buffer zones around South Ossetia and Abkhazia.

Russia has pledged to withdraw all its troops from Georgia proper by October 10, when the EU observers should be able to enter the buffer zones and monitor the situation. (dpa)