Several Iraqi militant groups have threatened to execute more than 20 hostages, including three Americans and 18 Iraqi soldiers, unless their demands are met before deadlines.

The Tawhid and Jihad group of suspected al Qaida ally Abu Musab al-Zarqawi set a 48-hour deadline for killing two US hostages and one British hostage unless Iraqi women prisoners were freed from Abu Ghraib and Umm Qasr jails, the Al Jazeera television said Saturday.

The group also said in a video obtained by Al-Jazeera that it would kill the captives if its condition is not met within before the deadlines.

US nationals Jack Hensley and Eugene Armstrong and British engineer Kenneth Bigley were taken hostage on Thursday by gunmen from their house in Baghdad's Mansour district.

An Islamist group said it would execute 18 soldiers from the Iraqi National Guard if a Shiite radical militia commander is not released within 48 hours, Al Jazeera reported Sunday.

Calling itself the Mohammed bin Abdullah Brigade, the group demanded the immediate release of Hazem al-Araji, an aide to Shi'ite rebel cleric Moqtada al-Sadr, who was seized Sunday in an overnight raid launched by US forces in Baghdad, the television said.

On Sunday, a militant group claimed to have beheaded three members of the Kurdistan Democratic Party (KDP) in Iraq for collaborating with the Iraqi government and posted a videotape of the killing on a website.

The Army of Ansar al-Sunna said in a statement that the three killed were taken hostage in Taji, north of Baghdad.

Speaking at a news conference on Sunday after talks in London with British Prime Minister Tony Blair, Iraqi Prime Minister Iyad Allawi vowed to hold the elections in January despite the surging violence in Iraq.