The security services of Russia and Belarus said Thursday that they will cooperate more closely to counter what they said were the West's "aggressive policies".
Russia's foreign intelligence service, the SVR, and the Belarusian Committee for State Security, known as the KGB, made the announcement in identical statements after their heads met in Belarus.
"In the spirit of traditional brotherly ties, Russia's SVR and Belarus's KGB agreed to conduct joint work to counter the destructive activity of the West aimed at destabilising the political and socio-economic situation across the Union State," the statements said.
SVR chief Sergei Naryshkin and KGB head Ivan Tertel stressed the "importance of consolidating efforts" to respond to global challenges and new threats, the security services said.
Russia and Belarus are part of a "union state" that links their economies and militaries. The countries have been discussing a closer integration as both of their ties with the West go from bad to worse.
Belarus strongman Alexander Lukashenko has for years had a volatile relationship with Moscow, playing it off against the West and ruling out outright unification with Russia.
But he has pivoted closer to the Kremlin since the breakout of historic protests against his nearly three-decade rule following a disputed election last August.
Lukashenko accused European countries of attempting to interfere in the ballot to sway its outcome and repeatedly said NATO was working to destabilise his ex-Soviet country.
But Belarus's strained ties with the EU hit rock bottom after Minsk last month diverted a Ryanair flight to arrest a Belarusian dissident onboard.
EU leaders have agreed to ban Belarusian airlines from flying to the bloc and recommended that EU-based carriers avoid Belarusian airspace.
Diplomats from the 27 EU nations are now working on expanding sanctions on Belarus and are eyeing hitting key sectors of the economy to try to undercut Lukashenko's financial backing.