Baghdad, Iraq ? Hardly a soul stirred on Thursday afternoon inside the warren of narrow dark alleys and side streets in Sanak, one of the capital’s busiest commercial districts. Shop after shop remained closed, their steel doors sealed with thick padlocks. Empty stalls, flanked by apartments filled with cowering residents, served as a silent coda to what had unfolded two hours earlier.

Gunmen in camouflage uniforms drove up in 11 cars about 10 a.m. and surrounded the area, just around the corner from an Iraqi police checkpoint, witnesses said. Some wore black ski masks, others black bandannas. They casually went from shop to shop, spending 30 minutes rounding up at least 25 shopkeepers, witnesses said. The men hustled their captives past the stalls, past customers, grabbing a few bystanders along the way.

“They took Sunnis, Shiites and Christians,” said Ziad Ali, one of the shopkeepers. “They did not differentiate. They even grabbed six boys.”

The mass abductions, brazen even by Baghdad standards, were the latest sign of worsening insecurity in the capital. Two days ago, 70 day laborers were killed in a car bomb attack in another busy district. A month ago, gunmen who claimed to be from the Shiite-run Interior Ministry seized as many as 150 people from an agency of the Ministry of Higher Education, which is controlled by a Sunni Arab party.

Thursday’s well-orchestrated kidnappings did not appear to be sectarian in nature or a reprisal attack, shopkeepers and officials said.

“This is very serious. This happened in the heart of Baghdad,” said Mohammed al-Askari, a Defense Ministry spokesman. “This is to create a state of chaos, so they can say the government has failed, the political process has failed. This is aimed at stopping life in the city.”

The assault occurred on a day when a U.S. congressional delegation, led by Sens. John McCain, R-Ariz., and Joseph Lieberman, D-Conn., visited Baghdad. McCain repeated his call to deploy more U.S. troops to Iraq, saying 15,000 to 30,000 more were needed to stem the sectarian violence and bring stability.

“The American people are confused, they’re frustrated, they’re disappointed by the Iraq war, but they also want us to succeed if there’s any way to do that,” McCain told reporters inside the U.S. Embassy.

Meanwhile, Lt. Gen. Raymond Odierno began his duties as the number two U.S. general in Iraq, replacing Lt. Gen. Peter Chiarelli. Odierno told reporters that sectarian strife and car bombs were the main challenges to security in the capital. He reiterated views stated earlier by Chiarelli that a multipronged effort that includes economic, political and military measures were needed to contain the violence.

By Thursday evening, it was unclear how many people were abducted in Sanak, with estimates ranging from 25 to 70. Brig. Abdul-Karim Khalaf, an Interior Ministry spokesman, said that several of the victims were later released and that the investigation was continuing.