Updated

Arab television broadcast videotape Sunday of two men taken hostage by militants, one described as a U.S. Marine lured from his base and the other a Pakistani driver for an American contractor. Insurgents threatened to behead them both.

Also, militants hit a coalition transport plane with small arms fire after takeoff from Baghdad's (search) airport, killing an American passenger and forcing the aircraft to return. Turkey rejected demands by militants threatening to behead three Turkish hostages unless Turkish companies cease business with U.S. forces in Iraq.

Death threats against hostages as well as insurgent attacks on U.S. and Iraqi security forces have accelerated as Iraq's interim government prepares to assume sovereignty Wednesday.

The U.S. military confirmed that a Marine had been missing from his unit since June 21 but could not confirm whether he had been taken hostage. Militants displayed a Marine "active duty" identification card in the videotape aired by the Al-Jazeera (search) network.

In the video, the hostage had a white blindfold covering his eyes. He wore military fatigues, and his mustache was trimmed. The U.S. military said he was of Lebanese descent, though the Al-Jazerra report said the hostage's origins were Pakistani.

The kidnappers claimed to have infiltrated a Marine outpost, lured the Marine outside and abducted him. Al-Jazeera said the militants demanded the release of all Iraqis "in occupation jails" or the hostage would be killed.

They identified themselves as part of "Islamic Response," the security wing of the "National Islamic Resistance — 1920 Revolution Brigades." The name refers to the uprising against the British after World War I (search).

The group, which has claimed responsibility for previous anti-American attacks, first surfaced in an Aug. 12 statement claiming the United States was hiding its casualty tolls in Iraq to help President Bush's election chances.

U.S. officials believe the insurgency consists of several groups with different ideologies, among them Arab nationalists, former Baath Party members and Islamic extremists.

Earlier Sunday, the Pakistani driver was shown on a tape broadcast by a different Arab television station, Al-Arabiya. The hostage displayed an identification card issued by the U.S. firm Kellogg, Brown & Root, a subsidiary of Vice President Dick Cheney's (search) former company Halliburton.

Four masked men holding assault rifles across their chests said they would behead the Pakistani within three days unless Americans freed prisoners held at Abu Ghraib and three cities of central Iraq — Balad, Dujail and Samarra.

The gunmen said they captured the Pakistani near the U.S. base at Balad, 50 miles north of Baghdad. They did not say whether they were affiliated with any group,

The hostage, who gave his name as Amjad, urged Pakistani President Pervez Musharraf (search) to close the Pakistani Embassy in Iraq and to ban Pakistanis from coming to Iraq.

"I'm also Muslim, but despite this they didn't release me," he said, bowing his head. "They are going to cut the head of any person regardless of whether he is a Muslim or not."

It was unclear how either set of kidnappers was linked to Jordanian terror mastermind Abu Musab al-Zarqawi (search), who claimed responsibility for the decapitation deaths of American businessman Nicholas Berg (search) and South Korean translator Kim Sun-il (search) last week.

In Baghdad, meanwhile, an American soldier was killed Sunday when a rocket slammed into a U.S. base on the southeastern outskirts of the city, the military said.

Gunmen dressed in black killed six soldiers of the Iraqi National Guard, formerly the Iraqi Civil Defense Corps, and wounded four others at a checkpoint in Jalawla, 75 miles northeast of Baghdad.

In first reports of the attack on the transport plane, U.S. military officials said the aircraft was American. Later, however, Australia's Nine Network television said it was a C-130 transport from the Royal Australian Air Force. The plane was about 12 miles from the Iraqi capital when it was fired on and forced to return to Baghdad International Airport.

Australia Broadcasting Corp. radio reported that a passenger on the plane who died of injuries was a U.S. citizen. U.S. Brig. Gen. Mark Kimmitt also said the victim was believed to be an American, according to the report.

Attacks against coalition aircraft around Baghdad have occurred before, although no fixed-wing planes have been shot down. The main road linking the airport to central Baghdad also has become increasingly dangerous because of ambushes.

In Istanbul, Turkish Defense Minister Vecdi Gonul rejected demands by al-Zarqawi's group for Turkish companies to quit doing business with U.S. troops in Iraq to spare the lives of the three Turkish hostages.

"Turkey will not bow to pressure from terrorists," Gonul told two private television stations.

The demand was issued as Bush and other Western leaders gathered in Turkey for a NATO summit Monday. Turkey, the only Muslim nation in NATO, was put in a difficult position trying to balance alliance solidarity with national interests.

The U.S. mission in Iraq is deeply unpopular in Turkey, and it was feared that any killing of Turkish hostages could intensify anger against the United States.

More than 40 people from several countries have been abducted in Iraq since April — many of them released or freed by coalition soldiers. Several kidnappings have been blamed on the al-Zarqawi group.

In other developments:

— A U.S. Marine was killed in action Saturday in Anbar province, which includes Fallujah, Ramadi and other trouble spots, the military said Monday. About 850 U.S. service members have died since Bush launched the Iraq war in March 2003 to seize Saddam Hussein's weapons of mass destruction stockpiles, which have not been found.

— Three rockets exploded near one of Saddam's former palaces in Baghdad's Green Zone, the heavily guarded headquarters of the U.S.-run occupation, causing no damage or casualties. Later Sunday, guerrillas firing mortars in central Baghdad killed two children playing near a Tigris river bank, an Interior Ministry official said.

— In Mosul, mortar shells hit an office of the Patriotic Union of Kurdistan (search), a pro-U.S. political party. One party member was killed and nine others were injured. Also, gunmen killed a policeman in a drive-by shooting.