The four aid workers, two Canadians, a Briton and an American, were shown in the tape three days after they were snatched in west Baghdad.
The grainy video from a previously unknown group calling itself the Swords of Truth brigades showed four men sitting cross-legged on the ground.
It appeared to carry Sunday's date stamp and had crossed swords in the top right-hand corner.
The organisation accused the men of being "spies working for the occupying forces" under the guise of working for a Christian group.
Al Jazeera did not say if the tape included a threat against the men's lives.
The four men work for Christian Peacemaker Teams (CPT), one of the few remaining aid groups operating in Iraq.
The video showed the passport of 74-year-old Briton Norman Kember, a retired professor and life-long peace activist who has been identified by the British Foreign Office.
Later the US and Canada-based Christian Peacemaker Teams said in a statement that American Tom Fox, 54; Briton Norman Kember, 74; and two Canadians, James Loney, 41 and Harmeet Singh Sooden, 32, were kidnapped in Baghdad Saturday.
In the statement, the group blamed the occupation of Iraq by US and British forces for the kidnappings.
"We are angry because what has happened to our teammates is the result of the actions of the US and UK governments due to the illegal attack on Iraq, and the continuing occupation and oppression of its people," the group said.
CPT has been operating in Iraq since 2002 and works with local people to provide a "peaceful presence" in the country.
German hostage
The tape of the hostages emerged on the same day that another group issued video of it holding German archaeologist Susanne Osthoff and her driver hostage.
The pair disappeared in Baghdad on Friday.
Unidentified kidnappers threatened to kill Mrs Osthoff and her driver unless Berlin stopped cooperating with Iraq's US-backed government, Germany's ARD TV reported.
Extracts from that tape showed three armed, masked figures surrounding two blindfolded people sitting on the ground.
More than 200 foreigners have been seized since the US-led invasion in 2003 and around 50 have been executed since 2004.
In the latest spate, six Iranians, four men and two women, and an Iraqi woman were abducted on their return from a Shi'ite holy site in the city of Balad on Monday.
The women were released soon after and Iranian television said late on Tuesday that the four men had also been freed.
Police said two prominent Iraqis had also been kidnapped.
Saad Albana, a senior official in the Housing and Reconstruction Ministry, was abducted from his Baghdad home.
Gunmen also abducted Thafer Migwil Hazza, a relative of deposed leader Saddam Hussein and a former Iraqi army officer, from his house in Saddam's hometown of Tikrit, police said.
Iraqis killed
Political slayings are also on the rise ahead of parliamentary elections in December.
Bashar Shnawa Gaber, a senior member of the Shi'ite Dawa party, was shot dead in Baghdad.
The Dawa party forms part of the ruling United Iraqi Alliance.
Sunni Arab politicians Iyad Alizi and Ali Hussein and a bodyguard were shot dead as they drove in Baghdad.
Two members of the Christian Assyrian Democratic Movement were shot and killed on Tuesday by gunmen as they put up election campaign posters in the northeastern city of Mosul.
In Fallujah, a Sunni stronghold west of Baghdad, witnesses said gunmen in several cars shot dead an influential Sunni Muslim scholar outside his mosque.
Two US soldiers were also killed when their patrol hit a roadside bomb north of Baghdad, the US military said, taking the toll of American troops killed in Iraq to 2,110.
Troop pullout
Despite the upsurge in kidnappings of foreigners and Iraqis and political and sectarian violence ahead of the elections, there have been predictions that US troops may soon start to withdraw as overall security improves.
With the elections seen as a landmark along the road to stability, Iraq's national security adviser said up to 30,000 of the 155,000 US troops in Iraq could leave in early 2006.
Mowaffaq al-Rubaie said local security forces have been performing better than before and a recent fall in guerrilla attacks marks "the beginning of the end of the insurgency".
"We have tipped the balance now to our favour and the momentum is only going to get better," Mr Rubaie said in an interview, when asked about American troop withdrawals.
His remarks appears to contradict assessments by US generals who say very few Iraqi units are ready to fight alone.
Nine killed
Nine Iraqis from a Shi'ite village northeast of Baghdad were shot and killed on Wednesday as they boarded a minibus to go to work on nearby farms, police said.
Two more people were wounded in the drive-by shooting in the village of Abu
Saida, northeast Baquba, police added.
Police initially said the Iraqis worked on a nearby US military base, but a local village official, Awad Nuri, told AFP they were employed on nearby farms.