BARTICA, Guyana — Guyanese soldiers and police fanned out in the jungles surrounding this bullet-pockmarked township yesterday, searching for gunmen who killed 12 in the second massacre blamed on gangs in recent weeks.

As security forces took up positions outside Bartica, townspeople mourned the victims, who included three police officers surprised in their station. Nine civilians also died in Sunday night’s deadly attack. The normally bustling enclave was a virtual ghost town yesterday.

No one immediately claimed responsibility for the rampage in the town of 15,000 people, where miners buy supplies before heading into the country’s interior to search for gold and diamonds.

The men armed with assault rifles invaded the town’s police station and made off with a cache of ammunition and weapons after killing the police officers. Witnesses said they fired indiscriminately for about an hour while people hid in their homes.

“I am still hearing those shots in my ears,” said Inspector Mike Sutton, who told the Associated Press that he heard the men kick open the station doors and start spraying bullets.

Arshraf Ali, an uncle of 23-year-old shooting victim Haseeb Ali, said he saw a few townspeople being shot with their hands raised in surrender. The killers also shot five people sleeping in hammocks. The Sunday night massacre came just three weeks after gunmen attacked the coastal village of Lusignan, killing six adults and five children.

The two deadly assaults have shaken the South American country’s security system and raised concerns about the efficiency and alertness of its police force.