PODGORICA, Montenegro (AP) — Montenegro banned 87 Serbs from entering the country on Wednesday, saying they posed a security threat ahead of a European Union summit with Western Balkan leaders.

The men arrived in the coastal town of Tivat on a charter flight from Serbia earlier in the day. Police said they singled out the Air Serbia plane as part of increased security checks ahead of the summit on Friday that will gather top EU and Balkan leaders.

“As part of the activities aimed at preserving a stable security environment, the security services identified persons of security interest,” Montenegro ‘s police and its National Security Agency said in a statement.

The security agencies had “gathered operational data and intelligence that indicate without a doubt that the presence in Montenegro of the individuals in question would pose a risk for internal and national security,” according to the statement.

The men had communication equipment and banners reading ‘Serbia wins,’ which is campaign slogan used by the populist Serbian President Aleksandar Vucic and his ruling Serbian Progressive Party, according to the photos provided by the police. Vucic is expected to attend the summit in Tivat, a resort town on Montenegro’s Adriatic Sea coast.

Media reports on Montenegro and Serbian claimed the men included known pro-government activists who have been accused of attacking student demonstrators during more than a year of street protests against Vucic.

Montenegrin police said some of the men had criminal records and had taken part in “numerous high-risk public gatherings.” Authorities in Montenegro also confiscated two buses.

There was no immediate comment from Serbia.

Vucic has recently refused to attend ceremonies in Montenegro marking the 20th anniversary of the country’s split from Serbia and has openly supported pro-Serbian parties in Montenegro that opposed the country’s entry into NATO and sought closer ties with Russia.

The Tivat summit will focus on the prospects for membership of the six Western Balkan candidate countries — Albania, Bosnia-Herzegovina, Serbia, Kosovo, North Macedonia and Montenegro. All are at different stages of the EU accession process.

The EU has recently sought to encourage reform in the candidate nations fearing growing influence of Russia and China.