(CNN) -- Government forces attacked protesters in Bahrain Saturday, according to a human rights group.
"Security forces have spent the day attacking protests in different parts of the country," the Bahrain Center for Human Rights said in a statement. "Many serious injuries were reported, including a 15-year-old boy who was hit directly in the arm with a teargas canister."
The group also said its president, Nabeel Rajab, was arrested before a planned march in Manama that was to be a show of solidarity with Abdulhadi Al-Khawaja, one of Bahrain's most prominent human rights activists.
Al-Khawaja was sentenced to life in prison in June for his role in the anti-government demonstrations that swept through Bahrain a year ago. He has been on hunger strike for more than 50 days in protest of his sentence.
On Friday, Amnesty International issued a statement calling on Bahraini authorities to release al-Khawaja amid fears that he is at risk of death.
A member of al-Khawaja's family told CNN they were informed that al-Khawaja had been taken to a hospital due to his deteriorating condition but were not allowed to visit with him.
CNN could not independently confirm the claims of attacks on protesters, but the Bahrain Interior Ministry confirmed the arrest of Rajab. The ministry said in a tweet that Rajab was arrested for "calling (for) participation in unauthorized rally & illegal gathering."
Meanwhile, a 22-year-old protester died early Saturday after a shooting that the main Shiite opposition party Al-Wefaq blamed on neighborhood militias loyal to the Bahraini regime.
The victim, identified by police as Ahmed Ismael Abdulsamad, died of a gunshot wound to the thigh, the country's chief of public security, Major-General Tariq Al Hassan, said in a statement released by the Interior Ministry.
The shooter was apparently driving a civilian car, according to the statement. The case is being investigated as a murder, police said.
Al-Wefaq blamed a group of men in civilian clothing for the death of the man, whom opposition activists described as a photographer who frequently brought a camera to demonstrations to document the events.
He was shot late Friday while attending a demonstration in the village of Salambad, Al-Wefaq said. The group cited eyewitnesses, who said Hassan was taken to a hospital where he died of his injuries early Saturday.
Demonstrations in Bahrain failed to gain the traction of other Arab Spring uprisings following a crackdown by the authorities in the island state, backed by troops from nearby Saudi Arabia and the United Arab Emirates.
In November of last year, Bahrain's Independent Commission of Inquiry issued a report that was highly critical of the authorities' reaction to the protests, which began in February 2011, spurred by uprisings in Tunisia and Egypt.
The independent commission, set up by Bahrain's King Hamad bin Isa al-Khalifa, found that between February and April of last year, 35 people had been killed as a result of the unrest there.
Demonstrators and Bahraini authorities have continued to clash in recent months, with the opposition accusing the government of using heavy-handed tactics.