Hundreds of pro-democracy demonstrators in Bahrain gathered Saturday in the capital, Manama, for a protest led by the Shi'ite-led opposition, defying a government ban.

The demonstration was organized by opposition groups led by Al Wefaq, a leader of the Shi'ite majority's protest movement.

Riot police blocked roads leading to the city center, forcing demonstrators to gather elsewhere. The protest ended peacefully.

Also Saturday, the United States expressed concern over continued violence in the Persian Gulf nation, as well as the fate of a Bahraini human rights activist, Nabeel Rajab, who was injured during a demonstration Friday.

The U.S. State Department spokeswoman, Victoria Nuland, said in a statement that U.S. embassy officials in Manama met with Rajab and urged the Bahraini government to refrain from using excessive force against protesters, as well as launch a full investigation into Rajab's case.

More than 40 people have died since the unrest in Bahrain began nearly a year ago. The protest movement is aimed at breaking the Sunni minority's hold on power in the Shi'ite majority country.

Bahraini security forces faced off against protesters through much of 2011 in a series of confrontations. Analysts say the protesters have drawn inspiration from the uprisings in Tunisia and Egypt.

In November, the head of a special commission probing the violence said the government used excessive force, including the torture of detainees, at the height of its crackdown on demonstrators in March 2011.

But the report concluded there was no evidence that Gulf-area troops committed human rights abuses, after Bahrain called in Saudi troops to help crush the protests.

Bahrain is an important U.S. ally and home to the U.S. Navy's 5th Fleet. Washington has taken a cautious line with authorities, urging the country's leaders to open more dialogue with the opposition.