MANAMA, Bahrain -- A prominent human rights activist in Bahrain was released from prison on Saturday after spending nearly two years behind bars.
Nabeel Rajab, who heads the Bahrain Center for Human Rights, was sentenced to three years in 2012 on charges of encouraging "illegal gatherings" tied to anti-government protests in the country.
Also on Saturday, thousands of people marched in a funeral for 15-year old Sayed Mohsen, who died during protests earlier this week in Sitra, south of the capital, Manama. The procession turned violent when mourners clashed with security forces nearby.
Police fired tear gas to disperse the crowd.
Mohsen's family and the country's main opposition group Al Wifaq said the teenager died after being shot in the chest at close range with bird shot -- a weapon commonly used by Bahraini police.
The country's Interior Ministry said police were investigating the circumstances of the death. The ministry said police in Sitra reacted after being attacked with firebombs Wednesday during a funeral procession of a man who had died earlier in a bomb blast.
"While the specific circumstances in which Sayed Mohsen was shot remain unclear, the use of force in policing public assemblies ... must conform to the requirements of necessity and proportionality; and firearms may only be used as a last resort," Amnesty International said in a statement.
The rights group urged an independent and transparent inquiry into the teenager's death.
An appeals court later reduced his term by a year.
After his release from prison, Rajab was greeted by dozens of supporters and stopped to visit his mother's grave before heading home.
The activist is a key icon for the protest movement against the Gulf Arab monarchy's Sunni rulers. Since 2011, the country's majority Shiites have been protesting, demanding greater rights and political freedoms.
A statement from the Bahrain Center for Human Rights said Rajab was imprisoned for "advocating peaceful demonstrations to defend the civil and human rights of all the citizens in the country."
Rajab told The Associated Press that he is happy to be out after more than 600 days in prison, and called for the release of all political prisoners. He said stability can only be achieved "through respect for human rights."
"After two years in prison, I see Bahrain's political environment as more difficult and still without a roadmap for real reforms," he said.
In mid-2012, Rajab was also sentenced to three months for his comments on Twitter about Bahrain's prime minister. His conviction was overturned on appeal during his prison sentence for taking part in protests.
The opposition in Bahrain, which is home to the U.S. Navy's 5th Fleet, claims that at least 100 people have been killed in the past three years of protests.