Warsaw said on Thursday it would not reopen more border crossings with close Russian ally Belarus until at least mid-November in a move intended to show solidarity with fellow NATO member Lithuania amid heightened security concerns.

Polish and allied air forces were activated as Russia struck targets in Ukraine, prompting temporary closures of Radom and Lublin airports.

Authorities have detained a Ukrainian citizen in Poland and two others in Romania for allegedly working with Russian intelligence on a sabotage campaign.

Faced with an increasingly aggressive Russia and mixed messages from the US, Warsaw is ramping up its defensive capabilities

Russia is using cryptocurrencies to pay saboteurs carrying out hybrid attacks across the European Union, according to a Polish security official.

The road known as Via Baltica will pass through a narrow strip of land between Belarus and Russia ’s Kaliningrad exclave, called the Suwalki Gap.

Poland warned Russia's President Vladimir Putin on Tuesday against travelling through its airspace for a summit in Hungary with U.S. President Donald Trump, saying it could be forced to execute an international arrest warrant if he did.

Two suspects were also arrested in Romania for allegedly depositing incendiary devices at an international courier company in Bucharest.

The pair allegedly gathered intelligence on Polish military personnel and infrastructure, including transport hubs used to supply Ukraine with foreign military aid.

A Polish court handed down prison sentences to three Ukrainians on Friday for their roles in a string of huge fires in Poland and the Baltic states, as Warsaw aims to crack down on what it says is a wave of sabotage orchestrated by Russia.