At least one person has been killed and several others injured after riot police in Bahrain opened fire at protesters holding a funeral service for a man killed during protests in the kingdom a day earlier.
 
The victim, Fadhel Ali Almatrook, was hit with bird-shotgun in the Gulf state's capital, Manama, on Tuesday morning, Maryam Alkhawaja, head of foreign relations at the Bahrain Centre for Human Rights, told Al Jazeera.

"This morning the protesters were walking from the hospital to the cemetery and they got attacked by the riot police," Alkhawaja said.

"Thousands of people are marching in the streets, demanding the removal of the regime - police fired tear gas and bird shot, using excessive force - that is why people got hurt."

Meanwhile on Tuesday, the US said it was "very concerned" by recent violence in protests in Bahrain, a stalwart ally of Washington, and urged all sides to exercise restraint.

"The United States is very concerned by recent violence surrounding protests in Bahrain," state department spokesman PJ Crowley said in a statement. "We also call on all parties to exercise restraint and refrain from violence."
 
At least 25 people were reported to have been treated for injuries in hospital.

The crowds chanted "The people demand the fall of the regime!" as they poured into Manama's Pearl Roundabout after marching from the funeral on the city's outskirts.
 
An Al Jazeera correspondent in Bahrain, who cannot be named for his own safety, said that police took a very heavy-handed approach towards the protesters.
 
"Police fired on the protesters this morning, but they showed very strong resistance," our correspondent said.
 
"It seems like the funeral procession was allowed to continue, but police were playing a cat-and-mouse game with the protesters."

Royal apology
 
Later on Tuesday, the king of Bahrain, Sheikh Hamad bin Isa Al-Khalifa, made a rare television appearance in which he offered condolences on the protesters' deaths.
 
He expressed his condolences for "the deaths of two of our dear sons" in a televised speech and said a committee would investigate the killings.
 
"We will ask legislators to look into this issue and suggest needed laws to resolve it," he said, adding that peaceful protests were legal.

US spokesman Crowley said the country welcomed Bahrain's promise to investigate, and urged the government to quickly follow up on its pledge.

Police reportedly fired tear gas and rubber bullets at the funeral procession [Mahmood Nasser Al-Yousif]

Angered by the two deaths, al-Wefaq, Bahrain's main Shia Muslim opposition group, announced it was suspending its participation in the parliament.
 
"This is the first step. We want to see dialogue," Ibrahim Mattar, an al-Wefaq parliamentarian, said. "In the coming days, we are either going to resign from the council or continue."
 
Al-Wefaq has a strong presence inside the parliament and within the Shia community.

The protesters say their main demand is the resignation of Sheikh Khalifa bin Salman al-Khalifa, the prime minister, who has governed Bahrain since its independence in 1971.
 
An uncle of the king, he is seen as a symbol of the wealth of the ruling family.
 
The protesters say they are also demanding the release of political prisoners, which the government has promised, and the creation of a new constitution.

Tuesday's violence came a day after demonstrators observed a Day of Rage, apparently inspired by the recent uprisings in Egypt and Tunisia.
 
Thousands came out on the streets on Monday to protest, sparking clashes with riot police.

Video from YouTube showing riot police firing on largely peaceful protesters during that demonstration.
 
Poverty, high unemployment and alleged attempts by the state to grant citizenship to Sunni foreigners to change the demographic balance have intensified discontent among Bahrain's Shias.
 
Around half of the tiny island kingdom's 1.3 million people are Bahraini, with the rest being foreign workers. The majority of citizens are Shia.
 
Online reaction
 
Amira Al Hussaini, a Bahraini blogger who monitors citizen media for Global Voices Online, told Al Jazeera that there has been a huge outpouring of anger online in Bahrain.
 
"What we've seen yesterday and today, is a break from the normal routine - people like me, that are not necessarily in favour of the protests that are happening in Bahrain at this time, are now speaking out," she said.
 
"I am trying to remain objective but I can't - people are being shot at close range."
 
Hussaini said that people in Bahrain were very afraid.

"We are afraid of going out in the streets and demanding our rights. Tunisia and Egypt have given people in Arab countries hope - even if you believe that something is impossible.
 
"I personally have no respect for the police - they lie, they manipulate the story," she said.
 
"This is being pitted as a sectarian issue - the Shia wanting to overthrow the regime. But it is not a Shia uprising."

She said that people from all backgrounds and religions were behind the ongoing protests.