BAGHDAD, Nov 14: Gunmen dressed as police commandos kidnapped up to 150 staff and visitors in a lightning raid on a Baghdad research institute on Tuesday, the largest mass abduction since the start of the US occupation.

Hours later, the interior ministry said three of the kidnap victims were apparently set free and found unharmed along eastern Baghdad's Palestine Street.

Ministry spokesman Brig. Abdul-Karim Khallaf, told The Associated Press the police chief of the Karradah neighbourhood where the kidnappings occurred has been placed under investigation along with some of his officers.

The fate of the remaining kidnap victims remained unknown.

Iraq's higher education minister immediately ordered all universities closed until security improvements are made, saying he was ''not ready to see more professors get killed.

''I have only one choice which is to suspend classes at universities. We have no other choice,'' Abed Theyab said in an address to parliament. Theyab said he had repeatedly petitioned for more university security from the ministries of defence and interior, who command the police, but had received none.

Alaa Makki, head of the parliament's education committee, interrupted the body's session on Tuesday morning to say that between 100 and 150 people, both Shias and Sunnis, had been abducted in the 9:30am (0630 GMT) raid.

He urged the prime minister and ministers of interior and defence to respond rapidly, calling the abductions a ''national catastrophe.''

The kidnapping is the largest known of any group, although about 50 Shias were abducted from vehicles near Latifiyah, about 30 kilometers south of Baghdad, on Saturday, and a similar number taken from the offices of a private security company in March. The fate of those taken in those previous incidents remains unknown.

The kidnapping is the largest of any group since about 50 people taken from the offices of a private security company in March. Their fate remains unknown.

''It was quick operation. It took about 10 to 15 minutes,'' Theyab said. ''It was a four-story building and the gunmen went to the four stories.'' He said the gunmen had at least 20 vehicles, but possibly many more.

Makki said the gunmen had a list of names of those to be taken and claimed to be on a mission from the government's anti-corruption body to check on security ahead of a planned visit by the US ambassador. —AP