BAGHDAD, Nov 16 (Reuters) - Kidnappers who seized dozens of men from an Iraqi government building two days ago tortured and killed some of their hostages, the minister for higher education said on Thursday, citing the testimony of freed hostages.

The comments from Abd Dhiab, who also said some 70 staff were still missing, underlined the rifts in the government of Prime Minister Nuri al-Maliki, who has insisted that all but a handful of around 40 hostages have been freed.

Tuesday's raid by gunmen in police uniform raised new fears that sectarian militias were out of control, despite U.S. calls for Maliki to disband armed groups loyal to his Shi'ite allies.

Briefing senators in Washington, the U.S. commander for the Middle East said Iraqi forces had responded well to the kidnap on Tuesday and police commanders had been dismissed. Gen. John Abizaid said he was optimistic Iraq could be stabilised as U.S. forces trained and equipped their Iraqi counterparts.

He cautioned against suggestions from the new Democratic congressional leadership for setting a timetable for U.S. withdrawal but said the 141,000 U.S. troops now in Iraq were sufficient.

Higher Education Minister Dhiab told Reuters on Thursday that around 70 hostages had been released out of about 150 staff and visitors originally seized from one of his ministry's buildings in central Baghdad.

"There are a number of people who were killed, they are employees and guards," Dhiab said, without specifying how many.

"According to the people released, they were killed by torture," he said, adding that several of those released were in shock after being tortured themselves.

Dhiab, a member of a Sunni Arab party in the Shi'ite-led government, reaffirmed his determination to boycott the government until all the hostages are released.

With momentum growing in Washington for a change in tack to force Iraqis to impose order and bring U.S. troops home, Maliki has played down Tuesday's daylight raid. He left Baghdad for a two-day visit to Turkey on Thursday with several ministers.

MILITIA INFILTRATION

Dhiab has said the hostages were taken to a Shi'ite militia stronghold in Baghdad.

The father of one ministry employee who had said on Wednesday he feared for his son's life told Reuters on Thursday his son, a Sunni, had now been released.

A spokesman for the higher education ministry said officials were compiling a full list of names of those seized.

It included at least 100 employees of two departments in the building, as well as some 50 visitors. After the release of around 70 -- including 30 freed on Wednesday -- dozens were still unaccounted for, the spokesman said.

The main government spokesman, however, said on Wednesday that 37 people had been freed and only a handful were still missing.

In the latest spasm of violence on Thursday, gunmen opened fire on a bakery in mainly Shi'ite east Baghdad, killing nine people and wounding two, police said.

On Wednesday, an Interior Ministry source said 55 unidentified bodies, most of them tortured and shot, were found in Baghdad, and more than 40 other deaths were reported in Iraq.

On Thursday, the U.S. military reported the deaths of four U.S. soldiers, taking the number of U.S. deaths since the start of the March 2003 invasion to at least 2,863.

Dhiab said both Sunnis and Shi'ites, were among the hostages so far freed, joining other senior officials in playing down indications that the raid had a sectarian motive.

Several senior policemen were taken in for questioning after the raid, which raised questions about the extent of complicity between the U.S.-trained security forces and Shi'ite militias.

Recruiting and training over 300,000 Iraqis as soldiers and police has been a major part of U.S. strategy. But question marks hang over their competence and cohesion in the face of forces that are pushing Iraq towards civil war.

Gen. Abizaid, who met Maliki on Monday, said violence had eased since August, when he warned of civil war. It was too early to say Iraq had "turned the corner", however, and bloodshed was still at "unacceptably high" levels, he said.