An explosion killed three policemen in Bahrain on Monday during a protest in a village near the capital Manama, the Interior Ministry said, in one of the worst incidents of violence in recent months.
The United Arab Emirates said one of its police officers, serving in a Gulf Cooperation Council force operating in the island kingdom, was among the three dead officers, according to the UAE state news agency WAM.
The Bahraini Interior Ministry said on its Twitter account that a group of protesters had broken away from a mourning procession in the village of Daih and started blocking roads. The explosion took place as police were trying to disperse the rioters, it added.
There was no immediate word on what had caused the blast.
Both the UAE and Bahrain are members of the Gulf Cooperation Council, a political and military alliance that also includes Saudi Arabia, Qatar, Oman and Kuwait.
In 2011, Saudi Arabia and UAE sent forces to support Bahrain's rulers and quell pro-democracy demonstrators demanding reforms. However, small-scale demonstrations remain frequent and often lead to clashes with security forces.
The blasts occurred shortly after riot police attacked protesters with tear gas and sound grenades during their march to the capital’s Pearl Roundabout, according to Said Yousif, vice president of the Bahrain Center for Human Rights.
The roundabout, destroyed in 2011 by Bahraini police, was the focal point of Bahrain’s now three year old prodemocracy movement.
Demonstrators had initially gathered in the village of AlDaih to mourn the death of Jaffar AlDurazi, an activist who died while in police custody.
Opposition groups, including the main opposition group al-Wefaq, condemned Monday's blast and called on followers to ensure that protest activities were peaceful.
"They assert their rejection of any practice that targets lives and property and call on the people of Bahrain, demanding their just rights, to abide by peaceful means and to condemn these criminal acts," the opposition groups said in a statement sent to Reuters.
International human rights groups expressed concern that the blasts would be used as justification by authorities for further human rights violations.
Bahrain's government has been accused by several human rights organizations of subjecting opposition members to arbitrary arrests, harsh sentencing and torture.
Negotiations between the government and opposition aimed at ending the unrest have stalled.
While most demonstrations in Bahrain continue to be peaceful, random acts of violence have steadily increased in recent months, according to Brian Dooley, director of Human Rights Defenders program at Washington D.C.-based Human Rights First.
Dooley told Al Jazeera that mounting political frustration and aggressive government crackdowns are contributing to the spike in violence.
Authorities say they have implemented some reforms and are willing to discuss further demands, but the opposition counters that there can be no progress until the government is chosen by elected representatives, instead of the ruling family.
A press release issued by Human Rights First soon after the blast said, "A real political solution should involve freeing political prisoners and civil society leaders who are still in jail. An inclusive political settlement should start immediately.”
Dooley accused Bahraini authorities of using excessive force during clashes with demonstrators.
A State Department report released Feb. 27 detailed significant human rights abuses in Bahrain. "The most serious human rights problems included citizens’ inability to change their government peacefully; arrest and detention of protesters on vague charges, in some cases leading to their torture in detention; and lack of due process in trials of political and human rights activists, medical personnel, teachers, and students, with some trials resulting in harsh sentences," it said.
Dooley warned that previously unseen levels of violence may become a chronic problem if no progress is made on the political front. "There's a political vacuum in Bahrain and the longer the frustration mounts, the more likely people will turn to support wherever they can find it," he said.
Reuters. Amel Ahmed contributed to this report.