A decapitated body in an orange jumpsuit was discovered in the Tigris River (search) in northern Iraq, the U.S. military said Thursday, raising fears that it belonged to a Bulgarian hostage killed the day before.

The identity of the body, discovered by Iraqi police Wednesday night northwest of the city of Beiji, 170 miles north of Baghdad, was not known, the military said.

Police turned the body over to the U.S. military for identification, and the Bulgarian government said fingerprints had been sent to Bulgaria for possible identification.

Militant groups in Iraq have taken several foreign contractors hostage, threatening to kill them if their governments did not pull their troops out or accede to other demands.

U.S. businessman Nicholas Berg (search) and South Korean translator Kim Sun-il (search) were wearing orange garments in videos showing their deaths.

A group affiliated with Jordanian militant Abu Musab al-Zarqawi (search) said Wednesday it had killed a Bulgarian hostage. Video broadcast on Al-Jazeera showed one of two Bulgarian hostages, later identified as Georgi Lazov, kneeling before three masked men.

Lazov was not wearing an orange jumpsuit in the footage shown, but the television declined to broadcast the rest of the video, which it said showed the man being killed. His body had not been recovered.

The militants also had threatened to kill a second Bulgarian hostage if its demand for the United States to release Iraqi detainees was not met.

"We know a body has been found, but it is not identified yet," Bulgarian Foreign Minister Solomon Pasi told reporters.

Speaking about the second hostage, Pasi said "the government has the duty to work on the assumption that he is alive, but the hope is diminishing with every hour."

Al-Zarqawi's group earlier claimed responsibility for beheading Berg and Kim. Berg's decapitated body was found near a highway overpass in Baghdad. Kim's body was found between Baghdad and Fallujah.

The militant group holding Filipino truck driver Angelo dela Cruz (search) captive said they would release him when the last Filipino soldier leaves the country, which should take place by the end of the month, according to a statement read Thursday on Al-Jazeera.

Dela Cruz also appeared in a video on the Arab television station earlier, saying he was coming home soon and thanking his government for agreeing to withdraw its peacekeepers from the country.

In the video, dela Cruz was no longer wearing the bright orange garment he had worn previously. He pointed out that he had changed clothing, an apparent sign that he is no longer under threat of execution.