Kuwait's public prosecutor Wednesday ordered opposition leader Mussallam al-Barrak to be held in custody after he was questioned for allegedly insulting the judiciary, his lawyer said.
"The public prosecutor decided to detain him pending further questioning later today," Humoud al-Hajeri wrote on Twitter after Barrak was questioned for several hours overnight, AFP reported.
Mohammad al-Jassem, another lawyer for the former MP, said his client was questioned for alleged slander and insults to the supreme judicial council and its chairman, Faisal al-Marshed.
Dozens of activists and former opposition MPs gathered outside the police headquarters where Barrak was held as opposition groups called for a public rally in Kuwait City later Wednesday.
Barrak was questioned over two lawsuits filed by the judicial council and Marshed over remarks he made at a June 10 public rally that were deemed offensive.
He had claimed that former senior officials including members of the ruling family had stolen tens of billions of dollars from public funds and engaged in money laundering.
Barrak, who also criticised the judiciary, charged that the former officials had deposited the funds in foreign banks including one in Israel.
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.
The claims plunged the oil-rich Gulf state into a political crisis that prompted the emir to call for calm and let the judiciary handle the issue.
Before being questioned, Barrak said the public prosecutor was not impartial because he is on the judicial council which sued him.
He also said the public prosecutor should have initiated the case by interrogating the former officials who allegedly plotted the coup and stole the money.
Most opposition groups are not represented in parliament after boycotting an election last July in protest at a change to the electoral law.
OPEC member Kuwait experienced the worst domestic political turmoil in its history between mid-2006 and last year.
During that period, some dozen governments were formed and parliament was dissolved six times.