Thousands of Kuwaitis demonstrated Monday night after the lower court sentenced key opposition leader Mussallam al-Barrak to five years in prison for insulting the emir.
Around 10,000 people gathered at Barrak's residence southwest of the capital Kuwait City and marched on the nearby central jail, where Barrak could serve his jail term, disrupting traffic at a major highway without any police interference.
Barrak, a nationalist former MP, was handed the jail term over remarks he made at a public rally on October 15 and deemed offensive to Emir Sheikh Sabah al-Ahmad al-Sabah.
Ahead of the march, 15 former opposition MPs and prominent activists repeated most of the speech for which Barrak received the jail term in a show of solidarity with him. They plan to do the same every day.
Criticising the emir is a crime in Kuwait that carries a maximum penalty of five years in jail.
Barrak earlier told supporters at his residence that the "ruling is illegal but I will give myself up to police if they come to pick me up."
Last week, Barrak's defence team walked out of court after the judge refused requests to hear defence witnesses who included the Kuwaiti premier and two former opposition MPs.
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The information ministry however defended the ruling and Kuwait's judicial system.
"Kuwait has a transparent and independent judicial system. All citizens, regardless of their position, are equal in the eyes of the law," the ministry said in a statement sent to AFP.
"Anyone accused of a crime in Kuwait will get a fair trial with a comprehensive legal defence and open appeals process," it said.
The verdict came two days after the Kuwaiti opposition threatened to stage street protests and call for civil disobedience if Barrak was denied a fair trial and jailed.
Barrak is also facing trial on several other charges including storming parliament and participating in protests.
Several opposition tweeters and former MPs have been sentenced to jail on charges of insulting the emir.
Kuwait's opposition has been staging protests to demand the dissolution of the parliament elected last December on the basis of an electoral law that had been amended by the emir.
The opposition charged the change was illegal and aimed at electing a rubber stamp parliament.