More than 800 hand grenades were discovered, together with a collection of fuses and mortars.
The origin of the munitions is unknown, but correspondents say many weapons were looted during the 1997 unrest in Albania, ending up in the hands of ethnic Albanian guerrillas in Kosovo and Macedonia.
Macedonia is holding general elections in mid-September - the first since last year's ethnic Albanian rebellion, and peacekeepers in Kosovo have recently made a number of arrests to prevent any cross-border infiltration before the vote.
Hidden underground
The ammunition was discovered on Monday by a team of Nato peacekeepers, the United Nations and local police.
The grenades and mortars were hidden in boxes under the soil and inside tree stumps in a wooded hillside close to Korbulic, said Master Sergeant Thomas Lott, who headed the team.
Forensic experts have now started a search for fingerprints.
Written text in the boxes suggested the ammunition was likely to have been manufactured in Albania, but no specifics were immediately known, Mr Lott said.
Macedonian elections
Kosovo is legally part of Yugoslavia, but has been administered by the UN and Nato since June 1999, following an 11-week bombing campaign that halted the crackdown by Serb forces on ethnic Albanians in the region.
Neighbouring Macedonia has seen growing tension ahead of the elections.
On Monday, two policemen were shot dead in western Macedonia, near the Albanian border.
The elections are intended to cement an international peace agreement signed last August to end a seven-month ethnic Albanian uprising.