MANAMA: Bahrain opposition groups has urged the government to embark on "serious" dialogue to end the Gulf kingdom's crisis, condemning a harsh crackdown on sporadic but defiant Shiite protests.

In a statement late Sunday five opposition groups, led by the main Shiite formation, Al-Wefaq, said the regime of the Sunni-led government should launch political reforms to get the small nation out of political deadlock following the harsh clampdown in March on a month-long pro-democracy protest.

The groups said they were in favour of "opening a serious dialogue with the regime to exit the current political crisis that is inflicting heavy losses on the country and people."

Following a meeting on Sunday, they said the dialogue should be focused on "implementing drastic and comprehensive political and constitutional reforms," dismissing the outcome of a national dialogue called for by King Hamad which they said excluded the opposition.

"It is not acceptable to talk about the outcome of the so-called 'national dialogue' as a suitable foundation for the wanted reforms because it is void of any real constitutional and political reforms" the statement said.

The groups include the Arab nationalist and leftist Waed party, whose Sunni leader Ibrahim Sharif remains in prison since the crackdown on protests and has been convicted along with other leading opponents of plotting to overthrow the regime.

The opposition groups also condemned the recent heavy-handed response to small protests breaking out in villages of the Shiite majority.

"We strongly condemn the campaign of collective oppression and terrorism practised by security forces against peaceful demonstrators," the statement said.

Bahraini security forces on Sunday fired tear gas and used batons to disperse several hundred Shiite demonstrators who gathered outside the capital Manama for the fourth day in a row.

Shiite youth groups had called for a series of protests on the Budaiya highway which links Shiite villages with Manama's former Pearl Square, the focal point of the month-long pro-democracy uprising crushed in March.

The crackdown comes after Bahrain's government promised reforms following the publication last month of a highly critical report of abuses by the security forces during the protests in February and March.