Poland will bolster security on its border with Belarus amid fears that the presence of Wagner mercenary forces may intensify what it calls hybrid warfare with its neighbor.

“We potentially have a new situation in Belarus with the Wagner presence,” Deputy Prime Minister Jaroslaw Kaczynski said at a press conference in Warsaw on Wednesday. “The situation is dangerous for Ukraine and it’s also potentially dangerous for Lithuania and us.”

Poland estimates that about 8,000 Wagner members will be present in Belarus, which may mean a “new phase of hybrid warfare, phase that is much more difficult than we observe now.”

The government in Warsaw has reported an increase in attempts by migrants from Africa and the Middle East to cross into the country from Belarus. It’s accused the government of President Alexander Lukashenko of purposefully aiding the process.

Poland plans to increase its military presence close to the border as well as build new defenses there, Kaczynski said, declining to elaborate.

Lukashenko brokered a deal between Wagner leader Yevgeny Prigozhin and Russia President Vladimir Putin to end the revolt that came within 200 kilometers of Moscow, allowing Wagner troops to move to Belarus as one of options.

The Belarusian monitoring group Hajun, which uses open-source data and information from local informants, hasn’t yet reported any preparations for hosting Wagner along the border with Poland or other NATO neighbors of Belarus.

The only place where a camp appears to be set up is an abandoned military base in the country’s center, some 75 kilometers (47 miles) south-east of Minsk, Hajun said on Telegram.

Even as the Wagner leader’s jet was detected landing in Belarus, his mercenary troops haven’t been arriving in the country as of evening of June 28, the group said.

Belarus’s assistance for migrants crossing the border is part of the Russian plan of attacking Europe, Polish Prime Minister Mateusz Morawiecki said on Thursday. He spoke before leaving for the European Union summit, where the Warsaw government plans to propose a plan to tighten protection of the bloc’s borders.

The ruling Law & Justice party has recently raised the subject of migration in its campaign before the parliamentary election in the fall as it criticizes the EU’s plan to spread the burden of hosting immigrants among the member countries. The party plans to hold a referendum around the time of the general vote to ask Poles about the issue.

(Updates with report by Belarusian monitoring group Hajun and comments by Premier Morawiecki.)