A prominent Kuwaiti blogger has gone on a hunger strike to protest his detention by authorities, who accuse him of insulting the ruler and inciting the overthrow of government, his lawyer said Thursday.

Mohammad Abdul-Kader al-Jassem, a journalist and blogger who is a staunch critic of the government, was detained Tuesday following a complaint from the office of Kuwait's ruler Sheikh Sabah al-Ahmad al-Sabah, according lawyer Attorney Abdullah al-Ahmad.

Jassem had refused to eat or take heart medicine since Wednesday night, the lawyer said.

There is no evidence to base accusations on, Ahmad said, adding that Jassem was being questioned for writings on his web site, blog and three political books he published after they were licensed by authorities.

A government spokesman could not be reached for comment.

On his web site, Jassem has directly criticized the ruling family. He had also called on the emir to remove the prime minister from office, questioning his policies and competence.

Kuwait, the world's fourth-largest oil exporter, boasts a free press but many writers and bloggers have been questioned and tried for libel. The emir is protected from criticism by the constitution.

Freedom of speech campaign group Reporters Without Borders called for Jassem's immediate release and for all charges against him to be dropped.

It said in a statement Wednesday that the new summons and interrogations for writings going back to 2006 made it obvious that Jassem was being hounded by the authorities.

Reporters Without Borders said Jassem was sentenced in April to six months in prison for slander against Prime Minister Sheikh Nasser al-Mohammad al-Sabah. The court suspended the sentence pending an appeal.

(Reporting by Diana Elias; Editing by Reed Stevenson)