BAGHDAD, Iraq (AP) - Gunmen in police uniforms raided bus stations Monday in central Baghdad, seizing at least 50 people, including drivers and passengers preparing to travel outside Iraq, an Interior Ministry official said.

The attackers also grabbed people working in the area, where several travel agencies are based and buses pick up passengers traveling mostly to Jordan, Syria and Lebanon, Lt. Colonel Falah al-Mohamedawi said.

The victims, including two Syrians, were herded into more than a dozen vehicles, according to witnesses. It was not known who was behind the attack.

"They took all workers from the companies and nearby shops," said Haidar Mohammed Eleibi, who works for the Swan Transportation Co. in the Salihiya business district.

He said his brother and a cousin were among those detained, along with merchants, passers-by and even a vendor selling tea and sandwiches. "They did not give any reason for it," he said. "Police came afterward and did nothing."

Another transportation worker, Amjad Hameed, said 15 cars belonging to police rushed to the area and began randomly seizing people.

"We asked them why but nobody replied," he said, adding that Iraqi forces and Americans came to the site afterward.

The dramatic attack came a day after masked gunmen stopped two minivans carrying students north of Baghdad, ordered the passengers off, separated Shiites from Sunni Arabs, and killed the 21 Shiites "in the name of Islam," a witness said.

Haqi Ismail, a 48-year-old electrician, told The Associated Press that the attackers ordered the Shiites to lie down, and before they opened fire, one shouted, "On behalf of Islam, today we will dig a mass grave for you. You are traitors."

In predominantly Shiite southern Basra, police hunting for militants stormed a Sunni Arab mosque early Sunday, just hours after a car bombing. Nine people were killed in the ensuing firefight.

The surge in attacks has dealt a blow to Prime Minister Nouri al-Maliki's pledge to curb sectarian violence. He also failed again to reach consensus Sunday among Iraq's ethnic and sectarian parties on candidates for interior and defense minister — posts he must fill to implement his ambitious plan to take control of security from U.S.-led forces within 18 months.