PRISTINA, Yugoslavia -- Six explosions rocked an ethnically-mixed village in Kosovo on Wednesday, injuring two U.S. soldiers investigating the blasts, the NATO-led KFOR peacekeeping force said.

The explosions in the southeastern village of Klokot damaged five Serb houses, most of them unoccupied with the exception of one where an elderly Serb man lived.

The man was not injured, a UN source told Reuters.

A spokesman for KFOR, which seeks to secure peace in the southern Yugoslav Province following the 1998-99 conflict, blamed "extremists" for the violence and vowed the force would do its utmost to bring those responsible to justice.

The two U.S. soldiers were part of a patrol which entered Klokot around 2 A.M. (2400 GMT) after hearing an explosion there, the first in a series of six, another KFOR spokesman, drew Anderson, said in a statement.

"On hearing the first of the explosions in Klokot a nearby KFOR patrol entered the village and two members of the patrol were injured by the third of the six explosions," he said.

The injured soldiers were taken to the main U.S. base in Kosovo for treatment. They were in stable condition.

"The cause of the explosions in Klokot are, at present, unknown. However, several uninhabited houses were damaged and one was destroyed," Anderson said.

Another explosion in a nearby village at about the same time was caused by a fragmentation grenade, the statement said. "No civilian casualties are reported in either village," it said.

Kosovo was placed under UN-led administration in the summer of 1999 after 11 weeks of NATO bombing drove Serb forces out of the province, populated mainly by ethnic Albanians.

The Serb minority was targeted in numerous revenge attacks by ethnic Albanians angry at years of Serb repression under ex-president Slobodan Milosevic, now standing trial at the UN war crimes court.

But international officials in Kosovo say such violence has decreased over the last year, hailing this as a positive sign for the peace process and the chances of ethnic reconciliation.

They hope some of the roughly 180,000 Serbs who fled Kosovo will soon be able to return to their pre-war homes.

"We feel that we have made significant progress in that area," KFOR spokesman Gordon Cooper said about the area where the explosions took place.

"These isolated acts, however, demonstrate that there are extremists who do not share our vision of making Kosovo a better place," he said in a statement.