A KUWAITI court has freed three Twitter users on bail after detaining them for nine days for allegedly insulting the ruler of the oil-rich Gulf state, a rights activist says.
A fourth tweeter however remained in detention as his case will be heard by a court on Sunday, the director of the Kuwait Society for Human Rights, Mohammad al-Humaidi, said on his Twitter account.
One of the tweeters was freed on bail of $US3550 ($A3440) and the other two on $US17,700 each, Humaidi said. Their trial is set for December.
The four were arrested on November 14 and held in police custody pending further investigation on accusations they wrote tweets deemed offensive to Emir Sheikh Sabah al-Ahmad al-Sabah.
Three other Twitter users, including a woman, had been arrested with them but only remained hours in custody before being each freed on bail of $US3550.
Kuwait has clamped down on opposition activists and Twitter users mainly on accusations of undermining the status of the emir as the country heads to general polls on December 1 amid a bitter political dispute.
Several former opposition MPs and activists are facing trial over similar charges. Public criticism of the ruler is illegal under the Kuwaiti constitution.