MITROVICA, Kosovo -- An EU customs officer in Kosovo was shot to death early Thursday in the tense, Serb-dominated north, the EU Rule of Law Mission said.

The incident took place during regular staff rotation when two EULEX vehicles came under fire from unknown attackers, the mission said in a statement. The hospital chief in Mitrovica, Milan Ivanovic, said the victim was shot in the chest and leg and was dead on arrival.

"I condemn in the strongest possible terms the attack that led to the death of the staff member," EU foreign policy chief Catherine Ashton said in a statement, adding that the dead man was Lithuanian. "The perpetrators must be brought to justice."

The EU mission has been overseeing the implementation of the rule of law in Kosovo, a former Serbian province that declared independence in 2008 but that remains tense because Serbia and Kosovo Serbs do not recognize the split.

Kosovo's president, Atifete Jahjaga, blamed the attack on "forces that want to destabilize Kosovo."

She said in a statement the attack happened as the country "is showing political maturity" ahead of the Nov. 3 local elections, the first such poll that should see the minority Serbs voting in an election run by the ethnic Albanian administration in Pristina.

Serbian Prime Minister Ivica Dacic also condemned the attack.

"This shooting is not only against EULEX, but against the future of the Serbian people in Kosovo," he said.

EULEX staff members have been manning checkpoints on the border with Serbia, which has angered hardline Serbs who view the border control as confirmation of Kosovo's independence.

Joint border patrols were negotiated in EU-brokered talks between Serbia and Kosovo. The former foes signed an agreement normalizing ties in April.