A video sold in Baghdad market stalls shows young insurgents firing a series of mortars and calling for the American infidels to be expelled.

To adjust their aim, the militants rely on a gadget that owes its appearance in Iraq to the 2003 U.S. invasion -- the cell phone.

Saddam Hussein outlawed mobile phones, determined to maintain an iron grip on his subjects. But as Iraq catches up with the world's information revolution, cell phones have become as common here as they are everywhere else in the world. They are increasingly being used as battle tools -- to set off bombs from afar, to target fire and to provide insurgents with instant communications.

Caught in the middle of the conflict raging between the insurgents and U.S. and Iraqi forces is the company responsible for bringing commercial mobile-phone service to Baghdad: Iraqna. With its catchy yellow Q emblazoned on hundreds of Baghdad storefronts, Iraqna (pronounced ee-RAK-na) was supposed to be the symbol of free enterprise in a new Iraq. But its tribulations since coming here in late 2003 underscore the difficulty of doing business in a nation at war, where the freedom of wireless communication often runs against security needs.

Almost half of Iraqna's 300 power generators -- a necessity in Iraqi cities, where blackouts are still a daily occurrence -- have been stolen.

Three communication sites were destroyed by bombs. Late last year, insurgents kidnapped two Iraqna engineers from Egypt and accused them of collaborating with the United States. Then, Iraqi security services raided Iraqna headquarters and briefly detained the company's head of security, accusing him of colluding with the insurgents.

"We're between the two fires, operating in the most dangerous spot in the world," said Shamel Hanafi, Iraqna's chief commercial officer, who was the company's first employee on the ground here and now co-manages the network. He sits in Iraqna's bunkerlike office, protected against suicide bombers by concrete walls and dozens of employees toting Kalashnikov assault rifles.

Some insurgents had accused Iraqna, a unit of Egyptian communications conglomerate Orascom Telecom Holding SAE, of helping security forces spy on their activities -- a charge Iraqna denies, saying it deliberately opted not to install equipment in the communications network that would have allowed it to track and store users' movements.

Despite pouring more than $180 million into Iraq, making it one of the largest private foreign investors here, Iraqna has had trouble delivering reliable service in Baghdad. From late last year through June of this year, the network was plagued by frequent outages that sometimes lasted hours or days, causing widespread resentment.

"All the Iraqis know that this is the worst provider in the whole world. You can't contact anyone at any time," grumbled Muthanna Anis, a vendor of cell phone accessories and one of Iraqna's 1.1 million clients.

Inundated with complaints, Iraqna officials blame the United States. U.S. forces have been using jamming devices to disrupt enemy communications during security raids and to neutralize mobile phones attached to bombs that may be waiting along the road when a convoy passes. When called, these phones work as detonators.

Iraqna officials say that American interference reached such massive proportions in recent months that it frequently knocked out their system.

"We understand the circumstances here, and we can accept some interference three or four hours a day -- but not around the clock, 24 hours," Hanafi said. "The customers don't understand. They think it's our mistake. People come here and complain, saying we stole their money, we're crooks."

U.S. military officials acknowledge that occasional jamming occurs but deny that they systematically disrupt Iraqi communications networks.

In Baghdad, fear of mobile phones is so widespread that U.S. and Iraqi security guards routinely order civilians to remove the batteries from their cell phones before approaching checkpoints. Wireless technology has made insurgent groups much more effective. For example, a mortar-firing team miles from its target can adjust its aim via mobile-phone contact with a spotter who can see where mortar shells landed.

Still, mobile phones often provide more reliable communications than the fixed-line telephone network, which was badly damaged in Baghdad by American bombing and subsequent looting in 2003.

Most Iraqi cell phone users have prepaid accounts that they can replenish with scratch cards.

Most U.S. officials and some Iraqis rely on a mobile-phone network managed by MCI Inc. that uses the 914 area code of Westchester County, N.Y. And Atheer Telecom, a mobile-phone company part-owned by Britain's Vodafone Group, has expanded into the Baghdad market in recent months, poaching clients unhappy with Iraqna's performance.

Iraq's mobile-phone licenses, issued when the nation was governed by the U.S.-led occupation authority in 2003, divided the country into three monopoly areas, initially restricting Iraqna to Baghdad and central Iraq and Atheer to southern regions. These limits were lifted last year, allowing competition. The licenses expire at the end of this year.

Iraqna has repeatedly taken jamming complaints to the Iraqi government, urging it to intercede with the U.S. military and to confirm for irate clients that interference goes on.

Nasi Abachi, the government's head of frequency management, said his team has responded to several Iraqna tips.

On at least one occasion, he said, the Iraqi investigators discovered a "clone" broadcast tower operating in central Baghdad that falsely identified itself as part of the Iraqna network. The result of such "intelligent jamming" was that all the phones in the area tried to abandon the real antenna and switch to the clone, causing a network overload and a massive disruption of service.

Investigators have no proof that U.S. forces operated the clone antenna, but no one else in Iraq is believed to have the technical ability to do so. "We have good reason to believe that what Iraqna is saying is right," Abachi said.

The company's increasingly public complaints seem to have had some effect. While jamming still occurs, it has caused "much less impact on the network" in recent weeks, Hanafi said.

Sarmad Ali contributed to this report.

An injured man talked on his mobile phone at the scene of a suicide car bombing in Baghdad on Sunday.