Thousands of Kuwaitis rallied against a court ruling scrapping legislative polls as the opposition called for a constitutional monarchy and a full parliamentary system.
"This is the beginning of the road to a constitutional monarchy," prominent opposition MP Mussallam al-Barrak told a large gathering that lasted until around midnight Tuesday to protest the court ruling.
This is the first time that Kuwait's mainstream opposition called for fundamental reforms, a demand usually made by youth activists.
Thousands of opposition supporters braved high temperatures at over 40 degrees Celsius (104 Fahrenheit) and gathered outside parliament in the capital Kuwait City to protest the court ruling.
In an unprecedented verdict last week, the constitutional court, whose rulings are final, declared February's legislative election, won by the opposition, illegal and reinstated the previous pro-government parliament.
It based its decision on the grounds that two decrees dissolving the previous parliament and calling for a fresh election, both issued in December, were found to be flawed.
The ruling also forced the government to resign on Monday after just over four months in office. It said the move was designed to pave the way to take the necessary legal action to implement the verdict.
"We call on the authorities to issue a new decree to dissolve the 2009 parliament," that was reinstated by the court ruling, Barrak told the crowds estimated by the organisers at around 30,000.
Islamist MP Faisal al-Muslim said opposition groups have agreed to fight the forthcoming election on the same platform which calls "for comprehensive constitutional and legislative reforms."
Obaid al-Wasmi, a member of the scrapped parliament, said the government must accept "fundamental constitutional reforms that must lead to forming an elected government and a full parliamentary system."
Under Kuwait's unique parliamentary system, the government is controlled by senior members of the Al-Sabah ruling family and unelected ministers and its formation normally is not in line with election results.
The oil-rich emirate has been rocked by a series of political crises since 2006 during which the government resigned nine times and parliament was dissolved on five occasions.