AFP: A prominent Sunni opposition leader in Bahrain pleaded not guilty Monday at the opening of his new trial for "promoting political change through forceful means", judicial sources in Manama said.

Addressing the Higher Criminal Court, Ibrahim Sharif said the charges against him were based on "assumptions" and not facts.

Sharif, who headed the secular Waed party, was freed on June 19 after spending four years in jail over his involvement in 2011 Shiite-led anti-government protests.

But he was re-arrested three weeks later for "violating the law".

The activist is accused of promoting "violent disorder" in a "direct attempt to undermine stability in the kingdom and overthrow the regime", in addition to other charges.

The next hearing will take place on October 12.

Sharif played a prominent role in the month-long protests and was later among a group of 20 activists tried for plotting to overthrow the Sunni rulers of Shiite-majority Bahrain.

Opposition sources say the activist was taken back to prison after he criticised the government during a ceremony for a victim of the unrest that has rocked the kingdom.

The opposition in Bahrain, which is home to the US Fifth Fleet, is pressing for a constitutional monarchy and an elected prime minister.

At least 89 people have been killed in clashes with security forces since 2011, while hundreds have been arrested and put on trial, rights groups say.