Kosovo's PM Albin Kurti after visiting a newly discovered possible mass grave site in the village of Kalluder. [Armend Nimani, AFP]

Kosovo authorities said Tuesday they had identified a third potential mass grave in the country's north, expanding investigations into a suspected 1990s war crime that have already uncovered the remains of 11 people.

Excavation work began last week in the area of Zubin Potok, with the initial dig since expanding -- officials believe there could be as many as 23 people buried near surrounding villages.

Following the discovery of remains at the second site on Monday, investigators now said they were also looking into starting a third dig.

"Due to the sensitive phase of the investigation, the Special Prosecutor's Office is unable to provide further information at this time," the prosecutor's office said in a statement.

The 1998-1999 war between independence-seeking ethnic Albanian guerrillas and Serbian armed forces killed around 13,000 people and left 4,000 missing.

Decades of work to uncover mass graves have found the remains of thousands, but 1,600 are still missing.

All the remains have been sent for DNA testing and identification, a process prosecutors warn could take months.

Police have also arrested three men from the local area in recent days on suspicion of war crimes, according to prosecutors.

The discovered remains most likely belong to "23 Albanians who have been violently abducted, executed" in the spring of 1999, acting Prime Minister Albin Kurti said on Saturday.