* Jail terms handed down for supporting Islamist militants
* Syrian conflict raises Saudi fears about radicalism (Adds conviction on Thursday of second group of 15 men)
RIYADH, March 20 (Reuters) - A Saudi court has jailed 28 men for security offences including material support to wanted Islamist militants, aiding terrorism and helping young men go to Iraq, Syria and Afghanistan to fight.
The conservative Islamic kingdom has sentenced thousands of its citizens to prison terms for similar offences over the past decade. Al Qaeda waged a campaign of attacks from 2003-6 inside the country, killing hundreds of people.
The growing role of militants in Syria has raised fear in Riyadh about a new wave of radicalism among its own citizens, and the government has issued stern new penalties for fighting abroad or supporting groups it says are extremist.
The detentions have angered some conservative Saudis, who fear they are being targeted for their religious beliefs, as well as among liberals who say the accused have not been given fair trials. The government denies such allegations.
A group of 13 men were sentenced on Wednesday to between three and 14 years in prison. Among them were nine Saudi citizens, two Jordanians, an Egyptian and a Syrian, the official Saudi Press Agency reported.
They were convicted of owning material that glorified al Qaeda, money laundering, and involvement in weapons training in militant camps, SPA reported, without giving details on where these were located.
A second group of 15 men, who were described by SPA as belonging to the same cell and included 14 Saudis and a Jordanian, were sentenced to jail terms of between 11 months and 16 years in prison on Thursday for the same offences.
Some were also convicted of financing militants in Iraq. Last week Saudi Arabia officially denied accusations by Iraqi Prime Minister Nouri al-Maliki that Riyadh supported Sunni insurgents in his country's Anbar province.
Al-Riyadh newspaper on Thursday reported that some of those sentenced on Wednesday had helped militants travel to Iraq, Syria and Afghanistan to fight alongside Islamist groups in civil wars.
Earlier this month, the government issued a list of groups it described as terrorist or extremist, including al Qaeda affiliates in Iraq, Syria and Yemen, the Muslim Brotherhood, the Shi'ite Muslim Hezbollah in Saudi Arabia and Shi'ite Houthi rebels in Yemen.
Last month it said moral or material support for such groups would incur prison terms of five to 30 years, while travelling overseas to fight would be punishable by sentences of three to 20 years. (Reporting by Angus McDowall; Editing by Sami Aboudi and Mark Trevelyan)