The purported hostage, speaking clearly with a British accent, identified himself as "Jason" and gave the date as more than two weeks ago. He sat under a sign in Arabic identifying the captors as "The Islamic Shiite Resistance in Iraq."
"My name is Jason. Today is November 18," he said, alternately glancing at the camera and downward, perhaps at a piece of paper. "I have been here now for 173 days and I feel we have been forgotten." No other hostage was shown.
A written statement featured on the video, aired by Al-Arabiya television, accused Britain of plundering the wealth of Iraq and demanded that British troops leave within 10 days. It did not say what would happen if the deadline was not met or when the countdown begins.
Britain's Foreign Office condemned the broadcast, saying it "serves only to add to the distress of the men's families and friends." British officials have not released the names of the kidnapped men, and have requested their identities not be disclosed by the media.
The kidnapping took place May 29, when about 40 gunmen in police uniforms and driving vehicles used by Iraqi security forces grabbed the four security contractors and a computer consultant from an Iraqi Finance Ministry compound. Suspicion has fallen on Shiite splinter groups that the United States believes have been trained and funded by Iran.
The video was posted as Britain prepares to hand over security control of oil-rich Basra province -- the last of four regions of southern Iraq it occupied after the 2003 invasion -- to the Iraqis in mid-December.
British troops withdrew in September from their last base in Basra city to an airport garrison on the outskirts, and half the 5,000 British troops in Iraq are due to go home by the spring.
One expert suggested a motivation for the rare broadcast of a video by a purported Shiite group could be to project the handover as a victory for the militia factions battling for control of the area.
"They're aware of countries who are already pulling their forces out," said Ben Venzke, the head of IntelCenter, a Virginia-based firm that tracks terrorist activity. "It can sometimes allow them to tie events to it and hold it out as a victory."
While Shiite militias frequently kidnap victims for political or sectarian reasons or for ransom, it is unusual for them to air such videos, which are more frequently used by al-Qaida in Iraq and other militant Sunni groups.
Venzke said the video appeared to have features usually employed by the Sunni extremists, including a deadline and specific demands such as leaving Iraq.
"It is rare for us to be seeing hostage videos from any of the Shiite groups," he said. "They certainly have taken hostages in the past, but they tend to be handled in a little different way than with the other nationalist or jihadist groups."
Two black-clad kidnappers flanked the purported hostage in the video, but they did not speak. Instead, a written statement said the five had "acknowledged and confessed and detailed the agenda with which they came to steal our wealth under false pretense of being advisers to the Finance Ministry."
The tape promised to "follow up with their confessions later."
The brazen abduction came during a period of intense sectarian violence. The bloodshed has since declined, largely because of an influx of American troops to the capital, a freeze in activities by the feared Mahdi Army Shiite militia, and a U.S. push to enlist local Sunnis to help in the fight against al-Qaida.
The U.S. military said Tuesday it had killed nine senior al-Qaida in Iraq members and captured 31 last month, including a Syrian identified as Abu Maysara who was described as a close associate of the terror network's leader, Abu Ayyub al-Masri.
But suicide attacks, bombings and kidnappings continue daily.
A suicide bomber on Tuesday blew himself up after approaching Iraqi and Kurdish security forces near a police station 70 miles northeast of Baghdad, killing at least eight people and wounding 30, police and hospital officials said.
The attack took place in Jalula, a religiously mixed city in Diyala province, a former al-Qaida in Iraq stronghold that has seen a dramatic turnaround.
Hassan Qadir, a policeman who was wounded in his hand, said he was buying a newspaper in a nearby book store at the time of the explosion.
"The books on the shelves started to fall on me," he said from his hospital bed. "While I was trying to flee, I saw the owner of the store dying, with blood pouring from his face and chest. It was a terrible scene."
An American soldier, meanwhile, was killed in a vehicle explosion during a recovery operation in Anbar province, west of Baghdad, the military said Tuesday.
In another development, the Iraqi Cabinet agreed Tuesday to ask the United Nations to extend the authorization for U.S.-led forces in Iraq through the end of next year, but it will be the last time, officials said.
The move was largely a formality as U.S. and Iraqi officials negotiate a new security framework as the American military begins to draw down forces.
U.S. Embassy spokesman Philip Reeker welcomed the move.
"This is a very positive process," he said at a news conference. "Iraq is increasingly able to stand on its own but will not have to stand alone."
Associated Press writers Sameer N. Yacoub and Qassim Abdul-Zahra contributed to this report.