Iraq said on Sunday that foreign Arabs took part in the killing of 22 mainly Shi'ite pilgrims in the Sunni Anbar province and accused other countries of trying to fuel sectarian tension in the war-damaged country.

Gunmen on Monday attacked two buses carrying Shi'ite pilgrims headed to Syria from the holy Shi'ite city of Kerbala, killing the 22 men while sparing 15 women, 12 children and two elderly men. Four of the victims were Sunni policemen who had hitched a lift with the Shi'ite pilgrims.

The execution-style killings, followed by an angry reaction to the arrest of eight suspects in Anbar by Shi'ite authorities from Kerbala, threatened to rekindle sectarian hostilities. Anbar is a Sunni heartland that saw some of the worst fighting in Iraq's war.

General Farouk al-Araji, Prime Minister Nuri al-Maliki's military chief of staff, said Arab foreigners were among those who carried out the killings.

"It was a well-prepared operation. Many outside parties took part in it," Araji said in a news conference.

"Some of those who did the operation were of Arab nationalities. Arab countries took part in this event through a large amount of dollars," he said.

Araji declined to name any country but said the suspects had confessed that other countries were involved.

Iraq's government on Saturday tried to defuse sectarian tensions over the killings by meeting tribal leaders and releasing four of the men suspected of carrying out the attack.
The other four are still under investigation.

"They are hired criminals ... They want to ignite discord and conflict among Iraqis," Araji said.

"But I would like to tell the Iraqi people that Iraq will not be divided as long as we are alive. This is a promise."

Sectarian tensions still simmer in Iraq more than eight years after the U.S.-led invasion that toppled Sunni dictator Saddam Hussein and pushed the country to the brink of civil war. Thousands of people were killed at the height of sectarian fighting in 2006-2007.

Iraqi officials have often accused neighbouring countries of meddling in their affairs and sometimes funding and arming insurgents and militia members.