Kuwait's emir consulted with his crown prince and prime minister after four nights of clashes over the arrest of a prominent opposition leader ahead of a mass rally later Sunday.
"The prime minister briefed the emir and the crown prince of the events that violate the constitution and the law," said an official statement cited by the state news agency KUNA.
Police have used tear gas and stun grenades against demonstrators, and the interior ministry has vowed to deal firmly with unlicensed gatherings.
An interior ministry statement blamed demonstrators for the violence, charging that unidentified men threw a petrol bomb at the jail where opposition leader Mussalam al-Barrak has been held for the past five days.
Opposition groups plan a huge protest march later Sunday to the courts in Kuwait City to press for the release of Barrak, a former MP whose trial is due to begin on Monday.
The public prosecutor on Wednesday detained Barrak for 10 days pending trial on charges of insulting the judiciary and slandering the head of the supreme judicial council, Faisal al-Marshed.
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The KUNA statement said the emir, Sheikh Sabah al-Ahmad Al-Sabah, called on everyone "to comply to preserve the country's security and stability".
The interior ministry said police arrested a number of protesters, while opposition activists said around 25 people have been rounded up since Wednesday.
The opposition has denounced the legal action against Barrak as unlawful and "politically motivated", but the emir on Sunday strongly defended the judiciary.
At a public rally last month, 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 himself questioned as a witness on Thursday.
Most opposition groups are not represented in parliament after boycotting a July 2013 election in protest at Kuwait's amended electoral law.