Manama, Bahrain: Thousands of anti-government marchers jammed a major highway on Friday as clashes broke out for a second day between security forces and protesters marking the anniversary of their uprising in the strategic Gulf nation.

The spike in violence is likely to put pressure on Shiite opposition groups as they engage in talks to ease the crisis with Bahrain’s Sunni-led government, despite objections from hard-line factions who want to topple the Western-backed monarchy.

In another sign of escalating tensions, police said they found a bomb wearing 2 kilograms (4.4 pounds) on the causeway connecting Bahrain and Saudi Arabia, which closely backs Bahrain’s monarchy. Police said bomb disposal teams defused the device, which officials said contained “highly explosive material.”

On Thursday, a 16-year-old male and a policeman were killed on the second anniversary of the Shiite-led uprising that seeks a greater political voice in the affairs of the kingdom, which is home to the United States Navy’s 5th Fleet.

Bahrain’s Shiites comprise about 70 percent of Bahrain’s more than 550,000 native-born population, but claim they face widespread discrimination and are blocked from key political and military roles. Nearly 60 people have died in the unrest. Some activist groups place the toll higher.

The protesters joined a peaceful march along a main highway linking the capital, Manama, with Shiite areas to the west. Breakaway groups, meanwhile, clashed with riot police in nearby neighborhoods and fired tear gas and stun grenades.

Main Shiite political groups opened talks this month with government and Sunni envoys to try to ease the crisis. Washington and other Western allies of Bahrain’s rulers have applauded the effort. But some Shiite factions oppose the dialogue, claiming it will not weaken the Sunni dynasty’s power.

Officials said policeman Mohammed Asif was fatally wounded from a “projectile” after attacks from demonstrators. An earlier statement blamed Asif’s death late Thursday on a “domestic terror act.”

Meanwhile, a separate investigation is under way into the death of the teenager. Activists said he was killed on Thursday by police birdshot fire.

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