The kidnappers of four Jordanians in Iraq have promised to release them Saturday because their relatives and fellow staged an anti-American demonstration as demanded of them, the brother of a hostage said late Friday.

The kidnapping became known Tuesday when Dubai Television broadcast a video tape showing four men holding their identification cards. A man off-camera said "all Muslim and Arab nations, especially those neighboring Iraq" should not cooperate with the Americans.

Mohammed Abu Jaafar, whose brother Ahmad is being held, told The Associated Press said he received a call from one of the purported kidnappers who said they were pleased by the television pictures of the protest in Irbid in northern Jordan.

"We decided to release them on Saturday morning," Abu Jaafar quoted the kidnapper as saying. The kidnapper said the hostages would be handed over at a Jordanian field hospital in Iraq or "we will escort them to the border," he said.

Jordanian Foreign Ministry spokesman Ali Al Ayed (search) said the government has instructed its embassy in Baghdad to investigate the kidnapping by a group calling itself "Mujahedeen of Iraq, the Group of Death." Insurgents have taken more than 70 foreigners hostage in Iraq in recent months in an effort to force their countries to withdraw troops and to hamper reconstruction work.

About 150 people took part in the protest, held after Friday prayers in Irbid and Khleifat, 55 miles north of the Jordanian capital, Amman. The protesters chanted "Death, death to America and Zionism" and "Victory for the Iraqi resistance."

Abu Jaafar (search) said the kidnapper provided Ahmad's full name, the registration number and the color (yellow) of his truck. He said the kidnappers had been calling him for two days on the mobile telephone of another of the hostages, Mohammad Ahmad Khleifat.

On Thursday, the kidnappers demanded that the families of hostages win their release by staging the demonstration, Abu Jaafar said.

Friday night, one kidnapper said the gang was holding five truck drivers, not four as previously reported, he said. The extra hostage could not be immediately explained.