A top court in Bahrain on Monday overturned a nine-year jail term against Shia opposition chief cleric Ali Salman, convicted of inciting hatred and calling for forceful regime change.

The court of the cassation ordered a retrial of the head of the Al-Wefaq political formation before the appeals court, said a judicial source in the Gulf kingdom.

Salman had been sentenced in July 2015 to four years in jail after being convicted of inciting hatred in Bahrain.

But the appeals court in May more than doubled his jail term to nine years after reversing an earlier acquittal on charges of calling for regime change by force.

Salman's arrest in December 2014 sparked protests in Bahrain.

The cassation court had rejected a request to release the cleric earlier this month.

His jail sentence is part of a crackdown on the Gulf nation's largest opposition group, which has been dissolved by a court order over accusations of ‘harbouring terrorism’.

Al-Wefaq had the largest bloc in parliament before lawmakers walked out in February 2011 in protest over a deadly crackdown on Arab Spring-inspired protests.

The crackdown on Wefaq has drawn criticism from UN chief Ban Ki-Moon and Bahrain's allies in Washington, as well as rights groups.

Hundreds of Shias have been arrested and put on trial since security forces backed by Saudi-led troops crushed in March 2011 month-long protests that demanded democratic reforms.

Authorities have also stripped at least 261 people of their citizenship since 2012, according to the Bahrain Centre for Human Rights, including the country's Shia spiritual leader Sheikh Isa Qassim.