In a related development, a man considered the spiritual mentor of Iraq's al-Qaida chief Abu-Musab al-Zarqawi has been freed, government officials told The Associated Press on condition of anonymity.
Military judges said on Sunday they rejected an appeals court decision in May to reconsider the guilty verdicts issued against the eight men during a trial that ended on 27 December 2004.
"This court insists on its previous ruling," said Colonel Fawaz Buqour as the eight defendants shouted "Allahu Akbar," or God is the Greatest, from the dock.
Defence lawyer Hamad Emoush said he will appeal.
The eight were among 11 others charged with possessing and intending to use explosives, plus conspiring to commit terrorist actions against the US embassy in Amman and Jordanian military bases near the eastern Iraqi border, where the group believed American troops were stationed.
But the same military court had acquitted the 11 of the conspiracy charge for lack of evidence.
No attacks had been carried out when police uncovered the plot in December 2002.
Tried in absentia
All 11, including three Saudis tried in absentia, were sentenced on 27 December to different prison terms ranging from 7½ years to 15 years. None of the defendants are suspected of belonging to al-Qaida, Jordanian security officials have said.
King Abdullah II is an ally of the
US in its 'war on terror'
Al-Zarqawi's mentor, Isam al-Barqawi, was released from jail last Tuesday, but an announcement was only made on Sunday.
The military court which upheld its verdict on Sunday acquitted al-Barqawi in the same trial last December, but he remained in jail without explanation.
The government officials who announced al-Barqawi's release declined to provide other details on the detainee who shared al-Zarqawi's jail block for four years, between March 1995 and 1999.
Both men were then freed under a general amnesty issued by Jordan's King Abdullah II. Al-Barqawi, also known as Abu-Muhammad al-Maqdisi, was later detained for another case, while al-Zarqawi left Jordan, the officials said.
Al-Barqawi lead prayers and issued directives to al-Zarqawi when both were in jail, said ex-convict Yusuf al-Rababaa, who was imprisoned with both men for three years in a separate matter.
From his cell in Jordan al-Barqawi wrote to al-Zarqawi last October asking al-Qaida's point man in Iraq to "spare the blood of fighters and Muslim money" until a more appropriate time to wage an all-out war. Al-Barqawi's message was posted on the internet.
Al-Rababaa and another prisoner familiar with al-Barqawi's writing style said the text could be attributed to him.