Kuwait's Islamist-led opposition took control of the Gulf state's parliament, making sweeping gains in a snap election on the back of a wave of public anger over corruption and political deadlock, results showed on Friday.

The country's ruler, Sheikh Sabah al-Ahmad al-Sabah, called the vote in December after dissolving the chamber in response to a deepening political deadlock that has stymied reform and held up vital development projects in the oil-exporting country.

Analysts said the results might only deepen political turmoil in the key U.S. ally if they embolden the opposition to push for constitutional changes and challenge the government, which is appointed by a prime minister hand-picked by the ruling family.

The opposition win will not resolve ongoing political and social tensions in Kuwait; indeed, tensions ... could worsen as the opposition demands a structural change in the political order, said Eurasia Group in a note.

Candidates from the loose opposition bloc took about two thirds of the assembly's 50 seats, eroding the position of Shi'ite parliamentarians, who had generally sided with the previous government. The opposition bloc, which had just over 20 seats before the vote, will control the state's fourth parliament in six years.

Kuwait's parliament is fully elected with legislative powers, something unique in a region ruled by autocrats who tolerate little dissent.

But the ruling al-Sabah family holds the key portfolios in the appointed government, members of which can vote in the assembly.

The country has not seen the kind of uprisings that have rocked other parts of the Arab world. But the electoral success of an Islamist-led bloc echoed a trend across the region.

There's obviously more traction now for the (Kuwaiti) opposition groups. You have kind of a momentum, said Shahin Shamsabadi, senior adviser at the Risk Advisory Group.

The vote left the assembly without any women parliamentarians. Four women, who are not aligned with the opposition and won seats in the last poll, all lost.

Those who were associated with the government were more likely to lose, whether they were men or women, and those who were confrontational were more likely to win, said Shafeeq Ghabra, a political scientist at Kuwait University, adding that liberal candidates had suffered for a similar reason.

I think the middle way lost and many of the liberals were in the middle.

OPPOSITION DIVIDED

The opposition had been tipped to expand its influence in parliament in the wake of its success in ousting the unpopular former Prime Minister Sheikh Nasser al-Mohammed al-Sabah, whom it accused of corruption.

That anger came to a head in November when protesters led by opposition MPs stormed the assembly demanding the resignation of Sheikh Nasser. Soon after, the emir dismissed his cabinet - the seventh line-up in six years.

An investigation by the public prosecutor into notably large deposits in the bank accounts of 13 pro-government parliamentarians gave a further boost to the opposition, which said the sums were bribes paid by ministers to MPs for their backing in the assembly.

Kuwaitis are now waiting for the resignation of their interim government and the appointment of another.

Despite the opposition's gains, a web of tribal and sectarian loyalties has often undermined the bloc's ability to come up with a clear programme.

A ban on political parties makes religious and kinship ties the easiest and most effective way of mobilising support.

That has also raised the risk of tribal and sectarian tensions. Earlier this week tribesmen torched the tent of candidate Mohammed al-Juweihel after he insulted their group. A day later they skirmished with police outside the office of a satellite television channel that was hosting his ally.

Tensions between Sunni Islamists and the Shi'ite population have also been re-energised by events in the wider region. Sunni Islamists themselves are also divided, between hardline Salafis, moderates, Muslim Brothers and independents, amongst other groupings.

Sixty-two percent of Kuwaitis cast their ballots on Thursday, up slightly from 58 percent in the previous election in 2009.

(Additional reporting by Mahmoud Harbi; Editing by Sophie Hares and Andrew Heavens)