The commander of Serbia's elite anti-terrorist unit testified at a war crimes trial of four men on Tuesday that he believed they were responsible for carrying one of the most brutal atrocities of the Kosovo war.

The four members of the notorious "Scorpions" paramilitary group are being tried for allegedly gunning down 19 civilians — including women, children and the elderly — in the northern Kosovo town of Podujevo in March 1999.

Only five children survived the massacre.

The killings took place at the start of the NATO bombing, which was launched to stop the Serbian onslaught against Kosovo's ethnic Albanian rebels. The air war lasted for 78 days, forcing Serbia to relinquish control over the region.

Spasoje Vulevic, who fought in Kosovo during the war and now heads the Special Anti-Terrorist Unit, or SAJ, said he did not witness the killings but arrived at the scene after hearing the shots.

"I heard frantic shooting coming from the direction of a house," he told Serbia's war crimes court. "When I saw what had happened, I started shouting and they (the accused) just bowed their heads."

Vulevic said that what he saw "clearly indicated" that the Scorpions were responsible for the killings. He described the paramilitaries — who fought alongside regular police and army — as "mentally unfit" and unprepared for combat.

Another former Scorpions member, Sasa Cvjetan, was convicted of the Podujevo killings in 2004, and sentenced to 20 years in prison.

Kosovo declared independence from Serbia in February.