BRUSSELS — Several European foreign ministers on Monday threatened to impose further sanctions against Russia if it fails to cooperate with Ukraine’s proposed peace plan and doesn’t stop the flow of arms and militants across its border into eastern Ukraine.

Russia is “conducting a propaganda war with full speed ahead and no signs of them closing the border,” said Swedish Foreign Minister Carl Bildt.

Armed militants and even tanks continue to cross the border into eastern Ukraine, he asserted. “If the Russians say they don’t know how to close borders, I don’t think that’s a particularly credible statement,” Bildt added.

In a joint statement, the European Union ministers urged Russia to withdraw its troops massed near the Ukrainian border and revoke the parliamentary authorization for the use of force on its neighbor’s soil.