Armed men seized official buildings in a city in eastern Ukraine on Saturday and hoisted the Russian flag, deepening a stand-off with Moscow which, Kiev warned, was dragging Europe into a "gas war" that could disrupt supplies across the continent. At least 20 men armed with pistols and rifles took over the police station and a security services headquarters in Slaviansk, about 150 km (90 miles) from the border with Russia. Officials said the men had seized hundreds of pistols from arsenals in the buildings. The militants replaced the Ukrainian flag on one of the buildings with the red, white and blue Russian flag. On a road leading into Slaviansk, other members of the group, armed with automatic rifles, set up a roadblock and checked vehicles entering the city, a Reuters reporter said.Ukraine is in the process of recapturing the buildings as of this writing, according to reports. The Associated Press offered some additional details about the individuals involved in the incident.