Zimbabwe's police have seized cars belonging to Prime Minister Morgan Tsvangirai's official escort and arrested his drivers for possessing beacon lights usually found on police vehicles, their lawyer said on Tuesday. The move is likely to escalate tension between Tsvangirai's Movement for Democratic Change (MDC) and President Robert Mugabe's Zanu-PF party at a time when the coalition parties and political rivals are trading blame for a spate of violent clashes that has injured more than a dozen people. The two drivers' lawyer, Kossam Ncube, said the men were returning from South Africa where they had taken two vehicles for maintenance at the weekend when they were arrested in the border town of Beitbridge. 'Threat' to national security Ncube told Reuters the drivers, employed by the government, had appeared in court on Monday and been denied bail after prosecutors said they were a threat to national security. A magistrate was expected to rule on Tuesday whether to release them. "The charges are that they had no authority to drive the vehicles with beacons," Ncube said. If convicted the drivers could face a fine or up to two years in prison. A police spokesperson said he was not aware of the arrest. MDC members have warned Mugabe to drop his Zanu-PF party's plans for an early election, saying the poll planned for this year could lead to a bloodbath.