We insist on effective measures

Srdjan Kerim, Macedonian Foreign Minister

In Macedonia, a policeman was killed as the rebels managed to trap a government convoy for several hours near the villages of Brest and Malino.

The incidents come as Nato considers deploying troops along the volatile Macedonian border with Kosovo.

Click here to see a map of the area

At least one policeman and one guerrilla died in an hour-long exchange of fire involving artillery and heavy mortars, following the ambush in Macedonia.

The group was in the area for talks with local Albanian leaders and to distribute food aid to families in the region.

The Macedonian authorities have yet again closed all the border crossings with Kosovo to prevent incursions.

Buffer zone

Nato has rejected a Macedonian call for a buffer zone between Kosovo and Macedonia.

Yugoslavia says it will move into the "dangerous" border zone

But Macedonia Foreign Minister Srdjan Kerim insisted in Brussels that Nato intervene in the border area.

"We don't insist on forms, we insist on effective measures," the minister said.

The military alliance has already decided to allow Yugoslav troops back into part of the buffer zone alongside Macedonia which divides Kosovo from the rest of Serbia.

Yugoslav officials said their troops would be ready to enter the zone in two days.

We want to prevent what can be limited, localised skirmishes becoming bigger or spilling over into the wider region

Nato chief Lord Robertson

Nato Secretary-General Lord Robertson said: "We want to prevent what can be limited, localised skirmishes becoming bigger or spilling over into the wider region."

The rebels have warned that opening the zone to Yugoslav forces will lead to a worsening of the violence.

The actions of rebels, who want to unite parts of Serbia and Macedonia where ethnic Albanians live, have attracted international condemnation.

Albanian President Rexhep Mejdani has described their activities as "totally unacceptable".