Election is part of a reform process launched in the island kingdom a decade ago
Bahrainis voted for a new parliament on Saturday at a time of rising tension in the small Gulf Arab kingdom.
Bahrain, headquarters of the US Navy's Fifth Fleet which patrols the Gulf, has a Shi'ite Muslim majority population but is governed by the Sunni al Khalifa dynasty.
Allies Saudi Arabia and the United States see the country as a bulwark against the regional influence of Shi'ite power Iran.
Polling stations closed at 1700 GMT, and results were not expected until Sunday. The main Shi'ite opposition group Wefaq said it expected to win all 18 seats it had contested, based on its own exit polls. There are 40 seats in Bahrain's parliament.
"It is clear now that all those constituencies will go to Wefaq," its leader Sheikh Ali Salman told reporters.
The run up to the vote was overshadowed by a broad security crackdown against some Shi'ite opposition groups in August that also targeted bloggers and human rights activists.
Next week, 23 men charged with plotting to overthrow the political system will appear in court for the first hearing in their trial.
Critics accuse Bahrain of apportioning its voting districts in such a way as to ensure the Shi'ite opposition will not have a majority in parliament.
Sheikh Ali said the number of registered voters in the 18 districts the Shi'ite opposition group had contested would represent 56 percent of all registered voters, even though the group would not have a majority in parliament.
The opposition said 1,000 voters in Shi'ite districts were turned away from polling booths after being told their names were not on the register. The government denied irregularities.
Foreign Minister Sheikh Khalid bin Ahmed al Khalifa told a news conference voting lists had been published in August.
He said: "It shows and proves that this democratic process is continuing, it's solid, it's strong."
Saturday's election was the third since the creation of the current parliament, which has limited powers since bills need to pass an upper house whose members are appointed by the king.
Bahrain, with 1.3 million inhabitants and no major oil and gas reserves, relies on foreign investment and tries to present itself as having a business friendly environment.
The level of participation in the election and any increase in street protests afterwards could be more telling than the actual results, where few changes are expected.
Many Bahraini Shi'ites say they face discrimination over state housing and jobs, a charge the government denies.
Some districts where candidates fail to win 50 percent of the vote could see a second round of polling next Sunday.
A reform process begun by King Hamad bin Isa al Khalifa a decade ago is closely watched in the region, especially after the 2003 US invasion of Iraq brought Shi'ites to power there.
Abdallah Hassan from the Shi'ite village of Karranah said he did not think the vote would address his community's grievances.
He said: "There is no change in Bahrain, whether you have elections or not ... The parliamentarians can't change the laws and the economic situation".
Another Shi'ite voter was optimistic for the longer term.
Umm S Ali, from the village of Kazarkan, said: "A new parliament takes time to work well. After the elections in 2014, 2018 we will see some results." (Reuters)