Prosecutors asked for the death penalty for the men, accused of handing over to Shi'ite Iran photographs of Yemeni security and military installations as well as ports and islands, the indictment said.
"During the period between 1994 and August 25, 2009, they undertook to spy for a foreign state and hold illegal communications with those working for Iran's interests," the indictment said. The men were arrested in July and August.
"They received support and funding to carry out intellectual and political projects serving Iranian interests, and submitted to them reports on the political, economic and social situation in the country," the indictment added.
Yemen, under international pressure to end its northern conflict with the Shi'ite rebels, sealed a truce with them in February to halt the long-running conflict that has raged on and off since 2004 and displaced 250,000 people.
Yemen jumped to the forefront of Western security concerns after al Qaeda's Yemen-based regional arm claimed responsibility for an attempted December attack on a U.S.-bound plane.
Western countries and Saudi Arabia want Sanaa to calm the situation in the north to focus on fighting al Qaeda, which the West fears is exploiting instability in Yemen to launch attacks in the region and beyond.
Yemen has accused clerics in Iran of backing the rebels, raising concern that the conflict could escalate regionally, especially after Saudi Arabia entered the war in November after rebels seized Saudi territory. Tehran has denied the accusation.
Rebels had accused Riyadh of allowing Yemeni troops to use its territory to launch attacks against them. Their incursion led to clashes in which at least 113 Saudi soldiers were killed.
Fighting between Saudis and the rebels has since ended.
REBELS CALL FOR HALT TO TRIALS
Rebels dismissed the spy case, and others like it, as political, adding that nearly 200 rebels and their supporters were currently facing trial on various charges linked to their roles in the northern insurgency.
"These trials are political, and if the authorities have accepted the peaceful choice, they should halt these trials and free all of the prisoners," a source close to the rebels told Reuters.
A family member of one of the defendants said his relative had initially been accused of receiving religious texts from Iran, which were confiscated during a raid on his home. But espionage charges were later added.
The men were also charged with participating in an armed gang to carry out missions for the rebels whom they supplied with arms received from unnamed parties, the Defense Ministry's online newspaper said.
Yemeni President Ali Abdullah Saleh, whose country is also trying to quiet southern secessionists, declared the northern war definitively over last month. While the truce has mostly held, implementation of its points has been slow.
Previous truces to end the northern war have not lasted and analysts are skeptical the latest ceasefire will last as it fails to address insurgent complaints of discrimination by the government.
In an effort to cement the truce, Yemen freed scores of Shi'ite prisoners last week after the rebels in March released 170 government soldiers and tribal fighters allied with the state.
Rebels had wanted hundreds more insurgents freed, but government sources said many of those still held were facing trial and could only be released following an acquittal or pardon.
(Reporting by Mohammed Ghobari; Writing by Cynthia Johnston; Editing by Charles Dick)
