PRISTINA -- Ethnic Serbian villagers have blocked roads and clashed with police in northern Kosovo as police units conducted sweeps aimed at cracking down on cross-border smuggling.

The October 13 violence left at least 20 people injured, including police officers, and renewed fears of wider violence and tension between Pristina and Belgrade. It also prompted a new warning from the European Union.

An RFE/RL crew that was covering the unrest, near the village of Rudare, was attacked by a mob that surrounded the taxi the journalists were traveling in and broke the crew's camera. The reporters escaped without injury.

Clashes were also reported in North Mitrovica, not far from Rudare, where trucks and other vehicles were parked on main roads, blocking traffic. Tear gas was fired to disperse crowds in North Mitrovica, and another nearby village, Zvecan.

At least eight people were arrested, Kosovar officials said. Of the 20 injuries, 10 were police officers, according to Sabedin Mehmeti, director of Kosovo's police.

Interior Minister Xhelal Svecla pushed back on assertions the sweep was aimed at local Serbs, saying that most of those arrested were ethnic Albanians.

"This operation is not directed against any nationality. This operation is directed against criminals who smuggled goods illegally in Kosovo," Svecla told a news conference.

In a statement earlier, the police said the violence broke out in the town of North Mitrovica when "criminal groups...created roadblocks with various means of transport, [and] used gas cylinders, shock bombs, gunfire and hand grenades, in order to prevent and attack customs and police officials who have been on duty."

The violence came just weeks after the resolution of another dispute between Kosovo and Serbia over license-plate requirements that were imposed by Kosovo.

Ethnic Serbs living in Kosovo balked at the new rules, and blockaded parts of the border. At one point, Serbia sent fighter jets and helicopters flying along the border, and Kosovo sent riot police to the region.

EU officials ultimately brokered an agreement between the two sides, and troops from the NATO-led peacekeeping forces in the country, known as KFOR, deployed to the region.

Prime Minister Albin Kurti, who won office pledging greater "reciprocity" in relations between Pristina and Belgrade, defended the police sweeps, and promised officials would continue cracking down on smuggling.

"Crime and criminal groupings will not be tolerated and will be fought," Kurti said. "We shall fight and prevent smuggling."

In Belgrade, Serbian Prime Minister Ana Brnabic demanded that the international community, including KFOR, help avoid "wider chaos."

"The situation is more than dramatic and this is the last moment in which a clear reaction is needed to stop the crazy policy pursued by Pristina," Brnabic said in a statement. "This kind of behavior has gone beyond any measure and leads us to the brink of chaos."

Serbian President Aleksandar Vucic was reportedly headed to the town of Raska, on the Serbian side of the border, for meetings with representatives of Serbian communities in Kosovo.

During the license-plate standoff last month, Vucic had threatened direct sanctions before the European Union brokered an agreement.

Serbia, which doesn't recognize Kosovo's 2008 declaration of independence, has imposed a similar requirement on Kosovar-registered vehicles for years.

A U.S. State Department spokesman called for calm following the clashes: "The United States urges calm in response to the events in Kosovo today. We will continue to work with EU and NATO partners to help all parties maintain progress in normalizing relations and reducing tensions."

The European Union's foreign-policy chief, Josep Borrell, called for an end to the violence.

"The violent incidents in the north of Kosovo need to stop immediately. Unilateral and uncoordinated actions that endanger stability are unacceptable," Borrell said on Twitter.

"All open issues must be addressed through the EU-facilitated Dialogue," he added.