AMMAN, Jordan — An al Qaeda-linked terrorist cell recently dismantled in Jordan was plotting to detonate a chemical bomb capable of killing thousands of people and to attack the U.S. Embassy and prime minister's office with poison gas, officials said Saturday.

Officials close to the investigation told The Associated Press that several terror suspects arrested in Jordan last month have confessed the plots were hatched by Jordanian militant Abu-Musab al-Zarqawi, thought to be a close associate of al Qaeda boss Osama bin Laden.

The officials, speaking on condition of anonymity, said the terrorist cell was planning to attack Jordan's secret service -- the General Intelligence Department -- with a chemical bomb that would have killed as many as 20,000 people and caused large-scale destruction within a half-mile radius.

Jordan's King Abdullah II said this week in a published letter of thanks to his intelligence chief, Gen. Saad Kheir, that the arrests of the terror cell members have "saved thousands of lives."

In his letter, Abdullah said that had the chemical bomb plot not been uncovered, Jordan would have seen "a crime that would have been unprecedented in the country in terms of the size of explosives mounted on the vehicles and the methods of carrying out the attacks or the civilian locations chosen."

On Saturday, the officials told the AP that the terror cell was also apparently planning to carry out simultaneous poison gas attacks against foreign diplomatic missions, including the heavily fortified U.S. Embassy in Amman, vital Jordanian public establishments like the prime minister's office and unspecified civilian targets.

They declined to elaborate, but stressed the plot had been foiled with the arrests late last month and earlier this month of an unspecified number of terrorist suspects.

Jordanian officials say the arrests occurred after suspected militants entered Jordan from neighboring Syria in at least three vehicles filled with explosives, detonators and raw material to be used in bomb-making.

Syrian officials have denied the claims.

Among those arrested last week were two Palestinian militants identified as Suleiman Darweesh and Muwafaq Adwan, thought to be close associates of al-Zarqawi.

Another Palestinian militant, Azmi al-Jayoussi, is thought to be at large.

U.S. officials have offered a $10 million reward for al-Zarqawi's capture, saying he is trying to build a network of foreign militants in neighboring Iraq to work on al Qaeda's behalf.

Al-Zarqawi is suspected of connection to about a dozen high-profile attacks in Iraq, including the bombing of the UN headquarters in August and Shiite religious ceremonies last month. Moroccan authorities believe he may have helped guide the Madrid train bombings. U.S. and Jordanian law enforcement say he funded the Oct. 2002 assassination of a U.S. diplomat in Jordan.

Jordan, a moderate Arab nation with close ties to America and a peace treaty with Israel, has been targeted by al Qaeda and other terrorists. Twenty-two Islamic extremists were convicted of plotting to attack U.S. and Israeli tourists during the kingdom's millennium celebrations.