It is aggression coming from Kosovo and we have proof

Macedonian Prime Minister Georgievski

US and German forces head the K-For peacekeeping forces in the eastern and southern sectors of Kosovo which border on northern Macedonia.

The prime minister's comments came as Macedonian forces pounded rebel positions around the city of Tetovo on the fifth day of fighting there.

Reserve call-up

BBC correspondent Peter Biles, who is in Tetovo, says a constant barrage of mortar and heavy machine-gun fire was being directed from government forces' positions, towards rebel strongholds in the hills.

Rebel roadblocks have been springing up around Tetovo

There has been little reported response from the guerrillas, who have threatened to spread the conflict, saying thousands of new recruits have travelled to the conflict zone to join up.

A Macedonian defence ministry spokesman announced on Sunday that the government had begun mobilising the army's reserve infantry forces as the crisis continued.

In his address to the nation, Prime Minister Georgievski announced other new measures against the rebels, including a curfew and restrictions on movement.

He said the army was using tanks and heavy artillery against the rebels near the village of Tanusevci, close to the Kosovo border.

Outside aggression

Mr Georgievski reiterated Skopje's position that the crisis was initiated by ethnic Albanians in Kosovo, and was not an internal conflict within Macedonia.

''It is aggression coming from Kosovo and we have proof,'' he said. ''This operation was well planned in advance in Kosovo.''

Macedonian protesters called for tough action

Across the border in Kosovo, Nato-led forces issued their toughest warning yet to the rebels that they wouldl face a strong response if any Nato bases inside Macedonia were threatened again.

A Nato base near Tetovo had to be evacuated when it came under fire on Friday, prompting Germany to deploy tanks inside Macedonia.

K-For commander Lieutenant General Carlo Cabigiosu said his forces would respond with "determination" to any further threat.

He said troops were now sealing the border between Kosovo and Macedonia in close co-ordination with the Skopje government.

New recruits

Guerrilla leaders in Selce, the group's headquarters near Tetovo, have said they plan to expand their territory, and are creating new branches across the country.

The BBC's Nick Wood, reporting from Selce, said young men were arriving every hour to volunteer as rebel fighters with the National Liberation Army (NLA).

Click here for a map of the region

Guerrillas have also been sealing off roads leading to Tetovo - in effect giving the NLA control of the high ground surrounding the town, says Nick Wood.

Officials say thousands of civilians have now fled Tetovo, the majority of whose residents are ethnic Albanians.

Officials say up to 2,000 Tetovo residents have fled

On Sunday, an estimated 10,000 people took to the streets of the capital, Skopje, to demand a tougher government crackdown against the rebels.

The rebels say they are Macedonian-born guerrillas who are fighting to improve the rights of ethnic Albanians there.

But some observers believe they ultimately want to unite ethnic Albanian communities in the region.

European Union foreign ministers are to meet in Brussels on Monday to discuss the crisis in Macedonia.

Meanwhile, the EU's security affairs chief, Javier Solana, is due in Skopje on Monday, and Russian Foreign Minister Igor Ivanov is also on his way to the region.