Countries bordering Belarus expressed concern on Thursday that a crisis over growing numbers of migrants trying to break through its frontiers into the EU could escalate into a military confrontation.

Lithuania, Estonia and Latvia condemned “the deliberate escalation of the ongoing hybrid attack by the Belarusian regime, which is posing serious threats to European security”, referring to charges that Belarus is using migrants as a weapon.

“This increases the possibility of provocations and serious incidents that could also spill over into military domain,” a joint statement by the Lithuanian, Latvian and Estonian defence ministers said.

Migrants stranded inside Belarus threw rocks and branches at Polish border guards and used logs to try to break down a razor wire fence overnight in new attempts to force their way into the EU, the authorities in Warsaw said on Thursday.

The EU may impose new sanctions on Belarus as soon as Monday after accusing Belarus of mounting a “hybrid attack” on the bloc by encouraging thousands of migrants fleeing war-torn parts of the world to try to cross into the bloc.