A group of Saudis have sent a petition to King Abdullah demanding the release of reform activists held since February on suspicion of what the authorities called "terror financing".

The Interior Ministry arrested 10 men it said had collected donations and given them to "suspicious elements", and officials suggested their actions involved helping insurgents in Iraq.

No formal charges have been laid, and lawyers and colleagues of the men say the arrests were in fact designed to scupper plans to set up a political party.

Saudi Arabia has no parties or elections to its parliament, and political life is dominated by the Al Saud family. "The detainees have taken part in peaceful campaigning since the Gulf war (to oust Iraq from Kuwait) and this contradicts the accusation that they are involved in violence," said the letter, dated Sept. 13, accusing the Interior Ministry of trying to tarnish advocates of constitutional reform.

"How does the Ministry imagine that people will believe the claim that they are involved in terrorism?"

IT said the government was behaving without regard for legal process as if it was above the law. Activists say prosecutors must extend detention without charge after the expiry of six months, file a formal indictment, or release the men.

An Interior Ministry spokesman was not immediately available to comment.

"We implore you, the Custodian of the Two Holy Sites, to take the initiative of releasing them," said the statement, signed by 135 Saudis who are family members and known democracy activists from a mixture of liberal and Islamist backgrounds.

King Abdullah is viewed by many Saudis as a supporter of some political reforms but diplomats say his room for manoeuvre is hindered by opposition from powerful members of the royal family. His half-brother Prince Nayef is Interior Minister.

A number of petitions calling for democratic reforms were presented to the authorities in 2003. King Abdullah released jailed activists when he came to the throne in 2005.