ISLAMABAD, April 10 (Reuters) – The United States has condemned the killing in Pakistan of three political leaders from a southwestern province, saying one of them had helped in the release of a kidnapped American U.N. official.

The United Nations expressed serious concern over the killing of the three men, the discovery of whose bodies in Baluchistan province on Thursday sparked violent protests. It called for an immediate investigation.

“We condemn the recent killings of three Baluch leaders,” the U.S. embassy in Islamabad said in a statement.

“One of the individuals played an active role in efforts towards the release of an American citizen and UNHCR official John Solecki.”

Solecki, 49, head of the U.N. High Commissioner for Refugees (UNHCR) office in Baluchistan, was kidnapped in the provincial capital, Quetta, on Feb. 2 when gunmen ambushed his car and shot dead his driver.

A previously unknown separatist group, the Baluchistan Liberation United Front, said it had kidnapped him and had demanded the release of prisoners it said were being held by the government.

Baluch nationalists have for decades campaigned for greater autonomy and control of the province’s gas resources. Baluch separatist militants have also waged a low-level insurgency.

Solecki was released last Saturday, shortly after the three Baluch leaders were taken away by unidentified men. Their supporters say they were taken away by security men.

The U.S. embassy said the role by one of the three leaders killed, Ghulam Mohammed Baloch, in efforts to secure Solecki’s released had been greatly appreciated.

“We call on Pakistani authorities to thoroughly investigate these three deaths and to bring those responsible to justice,” the embassy said.

“DISAPPEARANCES”

The provincial government said the killing of the three was an act of terrorism and ordered an inquiry. The military blamed an “anti-state element” bent on undermining reconciliation.

The three men were members of a committee recently set up by the government to investigate cases of disappearances, the United Nations said.

The human rights group Amnesty International said the government had failed to investigate an estimated 800 forced disappearances in Baluchistan over the past two years. It also urged authorities to investigate the killing of the three men.

A policeman was killed in rioting on Thursday when protesters set ablaze a bank and torched vehicles in Quetta and other towns.

There were no reports of disruptions at gas fields.

On Friday, a bomb planted on a motorcycle wounded four people while suspected separatists attacked a paramilitary vehicle with a grenade, wounding five soldiers, police said.

Baluchistan is Pakistan’s biggest province in terms of area but has the smallest and poorest population.

Taliban Islamist militants fighting in Afghanistan also operate out of Baluchistan but they have no links with the nationalists demanding autonomy or independence.

(Editing by Paul Tait)