Kuwait's opposition has vowed to escalate protests after three former MPs were jailed for three years for insulting the emir.
The case was the latest related to opposition activities since last summer, when an opposition-heavy parliament was disbanded on a legal technicality.
Fresh elections in December were boycotted by the opposition in protest against changes made to electoral law by emiri decree while parliament was out of session.
The former politicians Falah Al Sawwagh, Khaled Al Tahus and Bader Al Dahum were convicted this week of undermining the status of the emir, Sheikh Sabah Al Ahmad Al Sabah, at a political rally in October. Lawyers said they planned to appeal the verdict. By late yesterday, police had not taken the three men into custody.
In response to the verdict, which opposition leaders described as a political decision, thousands of demonstrators marched in protest on Tuesday.
"They want to terrorise us ... we will not surrender and will not be scared," Musallam Al Barrak, the opposition leader and a former MP, told supporters after they marched to the house of one of the convicted men.
Mr Al Barrak, who is also on trial for insulting the Emir, called on the country's major trade unions and youth movements to meet again last night to revitalise a coalition of forces opposing the government. More demonstrations were expected after the meeting.
"We are a country led by the rule of law and our constitution holds our emir to be inviolable," said the information ministry. "If our citizens wish to amend the constitution there is a straightforward legal way to do this, but we will not selectively enforce our laws."
One youth activist estimated that as many as 500 opposition supporters from various groups in the coalition were facing court cases for charges including defamation, spreading false information, and undermining state security.
This month a young activist, Mohammad Eid Al Ajmi, was jailed for five years for defaming the ruler. Two other youths, Ayyad Al Harbi and Rashed Al Enezi, were each sentenced to two years for anti-government comments on Twitter.
Kuwait's opposition coalition wants political reforms such as the legalisation of political parties and an elected prime minister.
But the recent flood of cases has left many prominent members of the oppositio distracted by the need to organise legal defences for themselves or colleagues.
Protests calling for democratic reforms and fresh elections that attracted tens of thousands in December appeared to have fizzled out and some analysts had predicted an end to the unrest.
But the latest convictions appeared to have regalvanised the shaky opposition coalition.
"This gives more reason for the opposition to keep focusing on the fundamental issue," said Shafeeq Ghabra, the former head of the American University in Kuwait. "The fundamental issue is the lack of reform, lack of political change, lack of ability to deal with the kind of demands that the Kuwaiti people are looking for."
Activists put the issue in even more stark language.
"The people want [the emir] to fix it," said a youth activist. "If you don't fix it your way, we will call for the fall of the regime."
* With additional reporting by Agence France-Presse and Reuters