RIYADH (Reuters) - Bahrain has arrested two men suspected of planting a bomb that killed a Bahraini woman in late June and of having received training and support from Iran, the interior ministry said on Tuesday. A ministry statement identified a third suspect in the blast but said he had fled to Iran, the Middle East’s Shi’ite Muslim power across the Gulf from Sunni Muslim-ruled Bahrain.

The bomb blast occurred on a road as the woman passed in her car in the village of East Eker, south of the capital Manama, on June 30, the statement said. Shrapnel hit the car, killing her and injuring her three children.

The statement accused the three men of receiving training in weapons and explosives from Iran’s Revolutionary Guards. One man traveled to Iran for his training, it said.

A Bahraini human rights group challenged the official version of events, citing “conflicting narratives”. Opposition activists have said on social media that witnesses reported seeing security forces fire on the woman’s car after it accidentally neared a royal convoy.

Bahrain, which hosts the Gulf-based U.S. Fifth Fleet, has been plagued by sporadic violence and bomb attacks largely aimed at security forces since 2011, when the government put down mass pro-democracy unrest by majority Shi’ites.

Bahraini accusations that Iran has fomented Shi’ite protests have been denied by Tehran.

The small Gulf kingdom is seen by its Sunni-ruled Gulf neighbors as a strategic bulwark against Iranian influence. It drew U.N. criticism last month when it acted to strip a top Shi’ite cleric’s citizenship and closed down the main Shi’ite opposition group.

U.S. Vice President Joe Biden called Bahrain’s king the day after the June 30 bombing to express “strong concerns” about recent developments in the country.