A man suspected of being al-Qaeda's number two in Yemen has gone on trial in the country's capital, Sanaa.
Ahdal is accused of receiving money from Osama bin Laden
Saudi-born Mohammed Hamdi al-Ahdal is accused of financing al-Qaeda and helping an armed group, as well as the deaths of 19 Yemeni security officers.
A second man, Ghaleb Abdullah al-Zayedi, is charged with hiding Mr al-Ahdal. Both men deny the charges.
The trial comes shortly after 23 convicts escaped from prison in Sanaa, embarrassing Yemeni authorities.
Proceedings began on Monday amid tight security in Sanaa. Approaches to the court were blocked by armoured vehicles.
Mohammed Hamdi al-Ahdal was captured by Yemeni security forces in 2003 after spending three years on the run.
His arrest was hailed by Yemeni and US officials as a major blow to al-Qaeda's operational capacity in the country.
USS Cole suspect
Yemeni investigators accuse Mr Ahdal of working directly for al-Qaeda's reputed former leader in Yemen, Qaed Senyan al-Harthi, who was killed by a US missile fired from an unpiloted aircraft in 2002.
The prosecution also blames him for the deaths of 19 security officers killed during the three-year manhunt.
Ahdal is thought to have fought in Bosnia and Chechnya
On his arrest US and Yemeni officials linked Mr Ahdal to the attack on the USS Cole, which killed 17 US troops in 2000.
It remains unclear whether he will face charges over that attack.
Reports have suggested that at least one man directly involved in the USS Cole attack was among the 23 men who escaped from prison on 3 February.
Another escapee was accused of attacking a French tanker in 2002.
At least 13 of the escaped prisoners were linked to al-Qaeda, prompting criticism by the US of Yemen's security procedures.