Bahrain's opposition called a rally near Manama on Friday marking the second anniversary of a Shiite-led uprising against the kingdom's Sunni rulers, a day after two people died when protests turned violent.
The mid-afternoon demonstration, to be held on the Boudaya highway that links a string of Shiite-populated villages with the capital, is likely to heighten tension in the kingdom which has seen two years of political upheaval linked to opposition demands for a constitutional monarchy.
The wave of protests and clashes that began on Thursday comes as members of the opposition engage the authorities in a new round of a national dialogue aimed at resolving the political deadlock.
Demonstrations on Thursday coinciding with the actual anniversary of the start of the uprising on February 14, 2011 turned deadly when a teenager was killed by police gunfire during clashes in a village near Manama.
Clashes raged sporadically in other outlying Shiite villages through the night and into the early hours of Friday, during which a policeman was killed after being struck by a petrol bomb, the interior ministry said.
"Police officer Mohamed Atef, hit by an incendiary device which seriously injured him, died soon after he was admitted to hospital," public security chief Major-General Tariq al-Hassan said in an interior ministry statement.
Protesters were hurling petrol bombs, iron bars and stones at police in the Shiite-populated village of Al-Sahla when the incident occurred, Hassan said.
The opposition identified the teenager slain on Thursday as Hussein al-Jaziri, saying he had been killed in the Shiite-populated village of Daih near the capital Manama.
Jaziri was "wounded by a shotgun that regime forces fired... He was severely wounded in his stomach and died at the hospital," said Al-Wefaq, the main Shiite opposition bloc.
The official BNA news agency said two police officers are being questioned by prosecutors over the killing, which the opposition described as "cold-blooded".
"The people are steadfast in getting their legitimate rights... for a democratic transition," said a statement by the opposition, which demands a full constitutional monarchy, an elected government and an end to confessional discrimination.
A number of groups, including Al-Wefaq, had called for strikes and nationwide protests on Thursday and Friday to mark the Arab Spring-inspired uprising that was crushed about a month after it began by the security forces led by troops from neighbouring Saudi Arabia.
The latest unrest comes amid a fresh round of a national dialogue between opposition groups and the government and political groups that support it.
The dialogue, hailed by the United States as a positive step that could bring reforms to satisfy all Bahrainis, resumed at the weekend for the first time since they broke down in mid-2011, with a second session being held on Wednesday.
The opposition is demanding that the results of the talks be put to a referendum and not be submitted to King Hamad for approval.
Its representative Sayed Jameel Khadim said agreement was reached in Wednesday's talks for the regime to act as "a main party in the dialogue and that its outcomes be turned into constitutional drafts".
The more radical clandestine February 14 Revolution Youth Coalition rejects dialogue and insists on overthrowing the monarchy in Bahrain, which is home to the US Fifth Fleet.
The two years of unrest have left at least 80 people dead, according to international rights groups, and many detained activists are on trial for their involvement in the unrest.
Amnesty International said on Thursday that Bahrain "cannot carry on imprisoning people simply because it can't take criticism".