Around 100 protesters and 11 policemen were hurt on Sunday as Kuwaiti riot police used tear gas and rubber bullets in clashes with tens of thousands of demonstrators, witnesses and officials said.
"The number of wounded protesters in hospital has exceeded 100 after riot police attacked them," director of the Kuwait Society for Human Rights Mohammad al-Humaidi said on his Twitter account.
The interior ministry said in a statement that 11 policemen were wounded after protesters threw rocks on them, adding that police only acted after protesters became violent.
Former opposition MP Abdullah al-Barghash told AFP he saw injured men being taken to hospital in ambulances.
Dozens of protesters were also arrested, some of them after they were beaten up in one of the most violent protests in Kuwait. Those arrested include former Islamist MP Waleed al-Tabtabai.
Barghash and other activists put the number of protesters at more than 100,000, which would be the largest gathering in the history of the Gulf state, but independent onlookers estimated the crowd at more than 30,000. Police made no estimate.
"The way demonstrators were dealt with is unprecedented in Kuwait," Barghash said as he led several hundred protesters, some wearing orange straps to signify the call for change.
Organisers of the "Dignity of a Nation" demonstration announced on its Twitter account the end of the procession more than three hours after it started.
Former Islamist MP Jamaan al-Harbash declared a victory for the people and a defeat for the regime and "these protests will not stop until the nation restores its dignity".
The opposition called the demonstration to protest against a decision by Emir Sheikh Sabah al-Ahmad al-Sabah to amend the electoral law. Activists claim the change is aimed at electing a rubber-stamp parliament.
"The people want to abolish the decree," chanted the protesters marching in the street which was blocked by riot police.
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The demonstrators were due to march on the Seif Palace which houses offices for the emir, crown prince and prime minister, but were prevented by police.
Organisers later asked protesters to gather at an alternative site in the capital where demonstrators cut off the country's key seaside Arabian Gulf Road for several hours.
Masked police in full riot gear repeatedly fired tear gas and sound bombs and later used rubber bullets to disperse the crowds led by former opposition MPs.
"It looks like a battlefield," Mohammad Rashed, a private sector employee, told AFP as he left the scene, accompanied by his wife and other relatives.
As the clashes took place, the emir received members of the Al-Sabah ruling family, in power for over 250 years, who reiterated their loyalty to him, official news agency KUNA reported.
The protest was called by the Islamist and nationalist-led opposition in protest at a the emir's decision to amend the electoral law, despite it having been confirmed by a court last month.
The opposition, which has decided to boycott polls called for December 1, said amending the electoral law amounted to a coup against the constitution.
In the latest clampdown on opposition leaders and activists, the public prosecution service issued an arrest warrant for a member of the scrapped 2012 parliament, Osama al-Munawer.
Munawer joins three former opposition MPs who have been in detention since Thursday. The prosecution on Sunday extended their detention by 10 days, according to Al-Humaidi al-Subaie, one of their defence lawyers.
Political tension has strongly impacted the Kuwait Stock Exchange which shed 3.05 percent at the start of the business week on Sunday, the biggest single day loss in more than three years.
The wrangling in the OPEC member has stalled development despite abundant oil-driven surpluses of more than $400 billion.