DUBAI: Bahrain's largest Shia opposition group said on Friday it would boycott parliamentary elections to fill seats vacated when its deputies resigned over the Sunni-led kingdom's crackdown on anti-government protests.

The move follows a “National Dialogue” that the monarchy -- which hosts the US Navy's Fifth Fleet -- organised to defuse tension after the crackdown, in which thousands were detained and allegations of torture were rampant.

The opposition bloc, Wefaq, pulled out of the dialogue as well, which led to the king expanding the powers of the elected parliament last month while reserving the broader power of an upper chamber that his court selects.

“We decided to boycott because we are no longer convinced of the authority of this parliament,” said Khalil al-Marzouq of Wefaq, whose 18 deputies resigned in February.

“It no longer had any popular legitimacy.” The elections are scheduled for September 24.

Wefaq's MPs quit as Bahrain moved to quash the protests, which were led by its Shia majority and called for broader political liberties and an end to sectarian discrimination. A few Shia groups sought to abolish the monarchy.

The kingdom in March called in troops from fellow Sunni-led monarchies Saudi Arabia and the United Arab Emirates to crush the protests, detaining more than a thousand people, at least four of whom died in custody.

Bahrain's Shia say they are systematically denied access to land and employment, and point to the naturalisation of Sunni Muslims from other countries, some of whom serve in the security forces, as proof of a policy of sectarian rule.

Bahrain hinted Shia Iran manipulated its co-religionists to spread unrest and sentenced several opposition figures to life terms for allegedly collaborating with a foreign power.

Two people face death sentences for the killing of policemen during the demonstrations.

The kingdom is now hosting a delegation of international law experts to investigate the protests and their aftermath.

Two former Wefaq MPs detained following the protests were released last week, as part of a group of 137 detainees set free. Some of those released may still face prosecution