Ali al-Dimaini, Matruk al-Falih and Abd Allah al-Hamad "took up issuing statements and collected as many signatures as possible on petitions" calling for changes in the country, according to a prosecution statement at their trial opening on Monday.
They were accused of "calling for adopting a constitutional monarchy and using Western terminology" in demanding political reforms.
The trio, who have been detained for nearly five months, also allegedly have questioned a provision in the basic law which says the king heads the "judicial authority".
Officials have accused the men of engaging in "incitement", sowing dissent, threatening national unity and having "some contacts with foreign sides".
The three men, who sat on the front bench of a packed courtroom, requested two weeks to study the accusations before entering their pleas.
But the judge, Muhammad ibn Khunain, banned three lawyers listed as members of the defence team from taking part in the trial "upon orders from the minister of justice". He did not elaborate.
A legal source requesting anonymity said the three lawyers had signed one of the controversial petitions.
Defence lawyer Muhammad al-Sinaidi requested the three defendants be released on bail, but the judge turned down the request which he said should be made in writing.
"We want a constitutional
monarchy like in other kingdoms ... . Jordan is a good example"
Saudi reformist on trial
Al-Falih, a lecturer at King Saud University, said before the session he and the other defendants had not been officially informed of the hearing, but only heard through unofficial channels on Sunday they would have to appear in court.
He said they had not been granted access to their lawyers until six weeks ago, but said their treatment in detention had been "OK".
Al-Falih reiterated his call for a constitutional monarchy in Saudi Arabia.
"We want a constitutional monarchy like in other kingdoms ... . Jordan is a good example," he said.
And the defendant downplayed a government decision to hold municipal elections later this year.
"Municipal elections is a limited step ... . It will not lead to [establishing a body] questioning the government," he said.
"We want to be able to elect the consultative [shura] council," he added.
Saudi Crown Prince Abd Allah has
pledged to reform cautiously
Al-Falih said the government could have instead announced a "reform package" including a date for elections for a legislative council.
The three defendants were among about a dozen of activists arrested on 16 March, half of whom were released within a couple of days after pledging not to lobby for reform in public.
Many of the activists who were detained were signatories to a petition demanding Saudi Arabia should become a constitutional monarchy.
Al-Dimaini, however, did not sign this petition.
The trial came on the same day that Saudi Arabia announced regulations for its first-ever municipal elections later this year.
Regulations issued by the Municipal Affairs Ministry stated all citizens under the age of 21 and military personnel would be barred from voting in the landmark polls scheduled for November onwards.
A constitutional law expert said the wording of the regulations in effect left open the possibility that women could vote.
It is unclear if women will be able
to vote in the municipal election
"The basic law in Saudi Arabia uses the masculine form when referring to citizens in general," Abd Al-Aziz al-Awaishiq said.
Saudi women rights' activists welcomed the new regulations as being free of any discrimination against women's right to cast their vote.
"If decision makers wanted to exclude women, they would have stated that clearly in the text," Hitun al-Fasi, a lecturer at King Saud University, said.
Women to vote?
Journalist Nahid Batahish noted that the regulations underlined the important role of women in Saudi society and that they were "partners in the process of development".
Earlier reports had said only men would take part in the process.
The government has recently eased some restrictions on women - allowing them to start businesses under their own name rather than that of a male relative - although influential voices in the kingdom have fiercely opposed the relaxation.
"If decision makers wanted to exclude women, they would have stated that clearly in the text [of the election regulations]"
King Saud University
The official SPA news agency said last Wednesday that the first nationwide polls in the kingdom to elect half the members of 178 municipal councils would be held in three stages from November into early 2005.
The other members of the new municipal councils will be named by the government.
The anticipated ballot is part of a drive to introduce limited reforms, which Riyadh insists must be tailored to Saudi specifications and not necessarily follow a Western pattern.
Saudi leaders promised last October to organise elections within a year, but an armed campaign by anti-government rebels raised doubts whether the timetable would be maintained.