The area had been quiet for more than two weeks, until Wednesday morning's bombardment, which reportedly continued until around noon.
The area had been quiet for more than two weeks, until Wednesday morning's bombardment, which reportedly continued until around noon.
The new clashes represent a second front in the three-month-old conflict between guerrillas and government forces.
On the conflict's other front, north of the capital Skopje, fighting flared again on Wednesday afternoon. There were reports of powerful explosions and gunfire.
Rebels have been occupying a string of villages there for the last three weeks.
Neighbouring Bulgaria has called for an international peacekeeping force to be sent to Macedonia, describing the situation there as worrying.
"We increasingly doubt whether the Macedonian authorities can handle the situation by themselves," said Bulgarian Defence Minister Boiko Noev.
Retaliation
The BBC correspondent in Skopje, Nick Thorpe, says there are fears that the rebels may be trying to reoccupy villages in the hills near Tetovo - the country's unofficial ethnic Albanian capital.
"We immediately sent reinforcements to the area," said a police spokesman. "We retaliated with force."
Trapped civilians
Macedonia's security council said on Tuesday that holding peace talks with the rebels was out of the question, and denounced them for refusing calls to disarm.
Though they say they are fighting to improve the situation of ethnic Albanians in Macedonia, they are widely believed to be seeking to join parts of the country to Kosovo or Albania.
Aid agencies say around 10,000 civilians may remain in the rebel-held villages in the north of the country, huddling in basements when they come under bombardment.
Ethnic Albanian political leaders have warned that they may plunge the country into an even deeper crisis if these civilians are hurt, by withdrawing from a broad coalition government formed last week.
Kosovo Albanians disarm
In neighbouring Serbia, ethnic Albanian rebels in the Presevo valley have agreed to continue their struggle by political rather than military means.
Hundreds have passed into UN-administered Kosovo in the past few days, handing in their weapons to Nato-controlled peacekeepers.
However, correspondents say that some hardline rebels may remain in the area.
Diplomats and Macedonian officials have expressed fears that some of the guerrillas could cross from Serbia into Macedonia to reinforce the rebels there.