BASRA, Iraq (Reuters) -Four Americans and an Austrian were taken hostage in southern Iraq when a civilian truck convoy they were guarding was hijacked after crossing the Kuwaiti border, their employer and Iraqi security sources said.

British troops cordoned off an area of the city of Basra on Friday in what the Iraqi sources told Reuters was a raid based on suspicion the five missing men were held there. A spokesman for the British forces policing the region declined all comment.

“The convoy was seized near Safwan yesterday,” one source told Reuters in Basra, 60 km (40 miles) north of Safwan and the border. Nine Iraqis were also abducted by the gunmen but at least some of the Iraqis had already been released, he added.

A source in a militant group in Basra told reporters that it was holding the foreigners, but he gave no details.

A company representative for the Crescent Security Group in Kuwait said all other people in the convoy its employeers were guarding had been accounted for and that the British forces were looking into the fate of the four Americans and the Austrian.

“We’re calling it an incident. We don’t know exactly what happened,” he said, adding that it occurred around noon (0900 GMT) on Thursday, 24 km (15 miles) north of Safwan.

The family of one American security contractor told a U.S. newspaper that U.S. officials said he had been captured after an exchange of fire in which there were no reports of casualties.

The convoy was heading for Nassiriya, 375 km (235 miles) south of Baghdad, along on a road that is heavily guarded to protect U.S. military convoys on what is the occupation force’s main supply route into Iraq, an Iraqi security source said.

Lieutenant Colonel Christopher Garver, a U.S. spokesman in Baghdad, said the military was still checking reports that the convoy might have been stopped at a bogus security checkpoint.

The brother of American Paul Reuben told a newspaper the State Department called the family to say he had been seized.

Hijackings and kidnappings for ransom are far from uncommon in the region and there are accusations of complicity between bandits, local police and the militias of Shi’ite Muslim parties which dominate southern Iraq and the Baghdad government.

There has also been friction between private security firms, which employ tens of thousands of foreigners in Iraq, and the growing Iraqi security forces. Earlier this week, police in Nassiriya said they had detained four foreign civilians working for a British company after they fired on a police checkpoint.

Foreigners abducted in the Shi’ite south have generally been released, unlike those seized further north where Sunni al Qaeda-linked insurgents have killed dozens of hostages.

However, anger at the U.S.-led occupation has grown among powerful Shi’ite groups, and attacks on British forces and private convoys bringing in supplies from Kuwait have increased.

Jennifer Reuben told the Minneapolis Star Tribune that her brother-in-law told her he was leaving Iraq because of safety fears: “They hate us here,” she quoted Paul Reuben as saying.

“They look you in the eye and say, ‘Go home, Americans.”‘

The incident comes at a time of heightened sectarian tension in Baghdad, not just on the streets but within the government and among groups engaged in the U.S.-backed political process.

The most prominent organization of Sunni religious scholars, the Muslim Clerics Association, called for the Shi’ite- and Kurdish-dominated coalition government to resign after it issued an arrest warrant for its leader, Harith al-Dari, on the grounds that he had engaged in “terrorism” and “sectarian sedition.”

Dari was in neighboring Jordan, a Sunni Arab state that is unlikely to extradite him. He told Reuters the government was trying to divert public attention from its own “crimes.”

Sunni leaders — and increasingly frustrated U.S. officials — complain that Prime Minister Nuri al-Maliki is not doing enough to rein in militias loyal to his Shi’ite allies and which were blamed for a mass kidnapping of dozens of staff from a Sunni-run government ministry on Tuesday.

Cabinet members are still at odds over whether up to 70 people are still missing and whether some were tortured and killed. In what one police source described as a possible reprisal, dozens of Shi’ite bus passengers were missing after suspected Sunni militants set up fake checkpoints in Baghdad.