JAKARTA (Reuters) - Security forces in Indonesia’s easternmost province of Papua are hunting for a separatist group suspected of killing at least 24 construction workers building a bridge in a remote district, a military spokesman said on Tuesday.

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Papua has suffered a simmering separatist conflict since it was incorporated into Indonesia after a widely criticized U.N.-backed referendum in 1969 and remains one of its poorest regions.

Colonel Muhammad Aidi said security forces were trying to reach the scene of the alleged attack in Yigi district after a priest had said that 24 men from the construction company PT Istaka Karya had been “sadistically slaughtered” by an armed criminal separatist group.

“According to the report we received, it started with an armed criminal separatist group holding a ceremony to commemorate what they claim to be their independence day on Dec 1,” Aidi told Metro TV.

Aidi said that one of the workers appeared to have taken a photograph which angered the group and sparked the killings.

Some Papuans regard Dec. 1 as their independence day from Dutch colonial rule, raising a banned separatist flag and holding rallies.

Aidi said the bodies of the construction workers were believed to be near the bridge they were building.

A join military and police team with more than 150 personnel was going in on foot after arriving at a nearby district, Papua police spokesman Suryadi Diaz said in a statement.

He said four wounded workers fleeing the area had claimed a military post was also attacked and a soldier killed.

Diaz said the armed group was led by Egianus Kogoya, a leader from the Free Papua Movement (OPM). The OPM could not immediately be reached for comment.

Indonesian Public Works Minister Basuki Hadimuljono told a briefing construction on the bridges to connect the Trans Papua road would be postponed until the area was secured.

Since coming to power in 2014, President Joko Widodo has pledged to hasten development and open up access to the resource-rich province including through the Trans Papua road project to link remote areas in the province.

Widodo on Tuesday ordered the military to guard construction workers in Papua and pledged infrastructure construction in the area would continue, according to comments on the website of the of office of the cabinet secretary.

While separatists have often been blamed for carrying out attacks, Indonesia’s human rights commission has also urged Widodo to end rights violations by security forces in Papua, an area where access by foreign media has often been restricted.