Nationalist Serbian lawmakers booed the European Union's top diplomat Federica Mogherini on Friday as she addressed their parliament during tour aimed at addressing concerns about rising tensions in the Balkans.
Mogherini's trip to all six Western Balkans states, still scarred by wars fought in 1990s along political, ethnic and religious lines, is meant to lay the groundwork for an EU foreign ministers meeting on Monday and a summit on Thursday.
Several EU leaders have expressed alarm at a variety of problems there and some blame Russia for seeking to destabilize the region, EU officials say.
At Mogherini's speech to the Serbian parliament, members of the Serbian Radical party chanted: "Serbia! Russia! We don't need the [European] Union!"
Four deputies from the nationalist Dveri party held banners reading: "Serbia does not trust Brussels."
Playing down the heckles during a speech that focused on the EU accession talks which Serbia hopes to complete by 2019, Mogherini later told reporters: "It is not nice to be rude to a lady!"
Prime Minister Aleksandar Vucic's pro-EU coalition has a comfortable majority in parliament but the popularity of pro-Russian nationalists is on the rise. In 2016, the Radicals returned to the Serbian assembly after several years.
Next Week's Summit
At their summit next week, EU leaders are expected to reaffirm their commitment "to support stability and to deepen political and economic ties with and within the region," according to an early draft of their joint statement.
That is despite weariness in EU states including France and the Netherlands where eurosceptic parties pose a challenge to the status quo in their own elections in coming weeks.
The EU has made Serbia's accession conditional on normalizing its ties with Kosovo but tensions have been on the rise this year. Serbia's ally Moscow refuses to recognize the 2008 independence of Kosovo, which has an association agreement with the EU.
Their neighbor Macedonia - which aspires to join both EU and NATO - has not been able to form a government since elections in December as the president has refused to give a mandate to a coalition that includes ethnic Albanians.
A genocide lawsuit that Bosnia lodged against Serbia at the International Court of Justice angered Bosnian Serbs as well as officials in neighboring Serbia.
In Montenegro, both pro-Western and anti-Western opposition parties are boycotting the parliament following a recent vote in which they say people were intimidated to back the government.
Russia opposes the accession of Balkan states into the EU has accused Europe and NATO of meddling in Macedonia's political crisis.
The EU believes Moscow is encouraging Bosnia's Serbs to seek independence and may have encouraged a move to unseat Montenegro's leader as he seeks to join NATO.
A border dispute between ex-Yugoslav EU members Croatia and Slovenia, adds to the mix of instability, EU officials say.