GEORGETOWN -- Unidentified gunmen late Sunday killed 12 people during a brazen assault on a police station at a gold-mining township in south-western Guyana, in the second massacre to have occurred in less than one month, authorities said.

Regional Chairman Hilbert Knights said three policemen and nine civilians were killed and several others injured.

He said preliminary information indicated that at least six men had arrived via the Essequibo River in a speed-boat and immediately invaded the Bartica police station located almost on the river bank.

Divisional Police Commander Gavin Primo said the gunmen who were dressed in military fatigues took with them weapons stored at the police station.

He said an undetermined number of persons were also injured and were receiving treatment at the hospital in Bartica, located more than 80-miles south-west of Georgetown.

Residents told Agence France-Presse that they had witnessed at least five of the civilians were ordered to lay face down on the ferry wharf before they were shot and killed.

A joint team of soldiers and police were deployed to the semi-forested and riverine area to track down the gunmen, state-owned television reported.

Sunday's incident came less than one month after the January 26 shooting of 11 people in their homes at Lusignan village east of Georgetown.

That incident was preceded by the shooting at the headquarters of the Guyana Police Force, resulting in two policemen being injured.