A seventh suspect accused in the terror plot remains at large.
Authorities have grown increasingly worried about the rise of extremism in a country with a strong presence of NATO peacekeepers, including hundreds of U.S. troops. Authorities had followed the alleged terrorist cell for three months after intercepting a call allegedly plotting an attack with another person of Kosovo descent in an unnamed European country, said the police official, who is part of a team that deals with terrorist threats.
Four of the suspects were arrested in a park in Pristina by undercover police agents posing as weapons dealers, the police official said. Another suspect was arrested in central Pristina and the sixth in the eastern town of Gnjilane. It was unclear whether a target had been identified and what the weapons were being bought for.
A sniper rifle, handguns and material for making an improvised explosive device were found in suspects' houses, according to the police official.
A justice official said the suspects had been watched by video surveillance, phone tapping, and email monitoring, but gave no further details because of the ongoing investigation. Both officials spoke on condition of anonymity because they were not authorized to discuss the matter.
Though the country of 2 million is overwhelmingly secular, ethnic Albanians from Kosovo and neighboring Macedonia have been linked with terror plots in the United States, including a foiled bombing last year in Tampa, Fla., and a 2007 attack on military personnel at Fort Dix in New Jersey.
Around 150 ethnic Albanians are believed to have joined foreign fighters battling the forces of Syria's President Bashar Assad and some 12 are believed to have been killed there.
The arrest warrant seen by the Associated Press said the 7 individuals identified as Genc Selimi, Nuredin Sylejmani, Valon Shala, Adrian Mehmeti, Musli Hyseni, Bekim Mulalli and Fidan Demolli are suspected of "preparing a terrorist act against the safety and constitutional order" in Kosovo.
The six will be detained for a month as the prosecution gathers evidence to bring formal charges. On Tuesday local media said police and justice officials received an email threatening to launch "painful attacks" on police if they do not release the suspects.
A defense attorney for Sylejmani said his client denied all charges. It was not immediately clear who represents the other suspects.
The Associated Press contributed to this story.