Tensions flared between Kosovo and Serbia over the weekend, raising fears of new unrest in the Balkans at a time when Western allies are focused on the Ukraine conflict.

KFOR, the NATO-led international peacekeeping force in Kosovo, said in a statement that it is closely monitoring the situation in Kosovo and is “prepared to intervene if stability is jeopardized.”

On the eve of the implementation of a law requiring them to replace their license plates with Kosovo plates, ethnic Serbs in northern municipalities of Kosovo bordering Serbia blocked roads and clashed with police.

The new rules, which were set to take effect on Monday, would have required Serbian ID and passport holders to obtain an additional document in order to enter Kosovo, as is already the case for Kosovars entering Serbia.

The European Union’s top diplomat, Josep Borrell, welcomed Kosovo’s decision to postpone the measures until September 1 and demanded that all roadblocks be removed immediately. The European Union’s special envoy, Miroslav Lajcak, expressed gratitude to the United States’ ambassador to Kosovo, Jeffrey M. Hovenier, in a statement posted on Twitter.

According to Kosovo police, no one was injured during Sunday’s protests, despite the fact that gunshots were heard in a number of locations, some of which were directed at police units. Protesters blocked roads leading to two border crossings by parking trucks and other heavy machinery.

Kosovo announced the month-long delay in implementing the new measures in a statement issued on Sunday, condemning “the obstruction of roads in the north of Kosovo and the firing of weapons by armed persons there.” According to the statement, the “aggressive acts” were instigated and planned by authorities in Serbia’s capital, Belgrade.

Russia’s invasion of Ukraine has heightened regional tensions. According to analysts, Russia’s nationalist and revisionist worldview has found a receptive audience in the region, particularly in Serbian President Aleksandar Vucic, Bosnian Serb political leader Milorad Dodik, and Hungarian Prime Minister Viktor Orban.

Serbia, a long-standing Russian ally, has rejected calls from the EU and the US to join sanctions against Moscow. Russia, along with China, continues to reject Kosovo’s independence and has condemned NATO’s war on its ally. In 1999, the Western military alliance launched a bombing campaign against targets in what was then Serbia and Montenegro in an attempt to halt Serbia’s onslaught against ethnic Kosovar Albanians fighting for autonomy.

On Sunday, Maria Zakharova, a spokeswoman for Russia’s Foreign Ministry, accused Kosovo of using new licensing laws and ID cards to expel the Serbian population.

“We call on Pristina, as well as the United States and the European Union, to stop provocation and respect the rights of Serbs in Kosovo,” she said, according to the Russian news agency Tass, calling the requirements “discriminatory.”

“If they dare to persecute, mistreat, and murder Serbs, Serbia will win,” Vucic declared at a press conference on Sunday. Albin Kurti, Kosovo’s prime minister, has accused Vucic of inciting the violence.