Police in Kuwait warned Friday they will deal firmly with any violence by protesters after two nights of confrontations with activists demanding the release of a detained opposition leader.
"The interior ministry affirms that any form of violence or riot will be dealt with firmly... and will continue to prevent such practices by using force," a ministry statement said.
Thousands of opposition activists staged noisy protests the previous two nights after the public prosecutor remanded prominent opposition leader Mussallam al-Barrak for 10 days pending trial on charges of insulting the judiciary.
The court on Thursday rejected a petition to free him and set July 7 for the first hearing.
The protesters marched on the central jail southwest of Kuwait City amid violent incidents with police using stun grenades and tear gas to disperse angry youths who blocked a major highway and other roads and stoned riot police.
The interior ministry said 13 people were arrested. The opposition accused police of using rubber bullets and said in a statement several protesters were wounded, at least one seriously.
Opposition groups have called for another demonstration late on Friday and for a huge protest in the capital on Sunday night.
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The opposition has denounced the legal action against Barrak as unlawful and "politically motivated".
The former MP is accused of slandering and insulting the supreme judicial council and its chairman, Faisal al-Marshed, in remarks made at a public rally on June 10.
Barrak alleged that former senior officials, including ruling family members, had stolen tens of billions of dollars from public funds and engaged in money laundering.
He also criticised the judiciary.
The scandal was later linked to claims that the same officials were seen in video footage plotting a coup.
Those allegations were made in a lawsuit filed last month by Sheikh Ahmad Fahad Al-Sabah, a senior ruling family member and former energy minister.
Sheikh Ahmad was questioned as a witness on Thursday night and afterwards said only that more interrogation would take place.
Most opposition groups are not represented in parliament after having boycotted a July 2013 election in protest at Kuwait's amended electoral law.