Updated

Thousands attended the funerals of five slain fishermen in Macedonia on Saturday as fears grew that the killings were ethnic-related. Authorities called it the worst case of mass murder in the tiny Balkan country since it gained independence 21 years ago.

The funerals in Radisani, a northern suburb of Macedonian capital Skopje, were held without incident, despite angry protests over the killings the previous day. Just north of Radisani in the municipality of Butel, where the killings occurred, officials declared a day of mourning and flags were lowered to half staff.

The victims, all ethnic Macedonians, were found shot dead late Thursday near an artificial lake at Butel. Four were in their 20s, and the fifth was in his 40s. Media identified the dead as Filip Slavkovski, Aleksandar Nakjevski, Tsvetanco Atsevski, Kire Trickovski and Borce Stefanovski.

Interior Minister Gordana Jankulovska said Saturday that "more than one perpetrator" killed the five men, using three types of firearms. She said that "by this point we (police) are still unable to say that the killings were ethnic-related because the police have no suspects."

Tensions have been simmering in Macedonia since the end of an armed rebellion in 2001, when ethnic Albanian rebels fought Macedonian government forces for about eight months, seeking greater rights for their community. The conflict left 80 people dead, and ended with the intervention of NATO troops.

Ethnic Albanians, who are mostly Muslim, make up a quarter of Macedonia's population of 2.1 million. Most residents are Orthodox Christian.

Jankulovska said "we are investigating all possibilities, even that this was a professional murder and that the murderers fled abroad. We have established contacts with the police in neighboring countries."

Riot police were deployed Friday on a highway leading to the village as dozens of angry youths blocked the road. A group among the mob smashed the windows of a vehicle belonging to a reporter for private TV station "24 News" and threw stones at passing buses.

Fears of ethnic conflict have moved officials, from President Gjorge Ivanov on down, to issue calls for restraint and a speedy investigation. The U.S. Embassy has urged "all parties concerned to remain calm, and to refrain from speculation or unfounded allegations."

There were two flare-ups of violence this year, the last one in March, with clashes between gangs of Albanian and ethnic Macedonian youths resulting in dozens of injuries. During several days of rioting, youths attacked buses and used iron bars, knives and baseball bats in street fights.