Macedonia sent reinforcements to an area near the border with Kosovo yesterday after eight members of its security forces were killed in the first serious violence since an ethnic Albanian insurgency was quelled a month ago.
An investigative team was trying to piece together exactly what had happened in what officials said was an ambush on a joint army and police patrol on Saturday by "extremists" near the north-west village of Vejce.
Six security force personnel were reported wounded as well as the eight dead, the highest casualty toll for a single incident since the conflict between security forces and the rebels erupted in the former Yugoslav republic in February.
The NATO Secretary-General, Lord Robertson, said violence would not work. "I condemn the cowardly acts of the extremists and my message is simple: the violence must end," he said.
The EU foreign policy chief, Mr Javier Solana, also condemned the outbreak of violence.
A senior Macedonian police official said it had already been clear that the recent peace did not mean a permanent end to the conflict which has sparked fears of a new Balkans war.
While officials did not name any particular group, Macedonian media pointed the finger of blame at the National Liberation Army ethnic Albanian guerrilla force.
President Boris Trajkovski of Macedonia held a late-night meeting with his defence minister, generals and police officials, and cancelled a visit to Romania.
Police and army movements could be seen overnight moving towards the village.