Reuters: Bahrain has detained five people behind a bomb attack in July that killed two policemen, the interior ministry said on Thursday, and accused them of being linked to Iran's Revolutionary Guards.

Sunni-ruled Bahrain, which has long accused Iran of stirring up unrest among its Shi'ite population, recalled its ambassador from Tehran last Saturday after what it said were repeated hostile statements made by Iranian officials.

Iran denies the accusations but openly supports opposition groups seeking greater rights for fellow Shi'ites, who are in the majority in the island kingdom.

The bombing outside a girls' school in the Shi'ite village of Sitra in July also wounded six other policemen and was the deadliest attack in Bahrain since March 2014.

The Interior Ministry identified a main suspect, 24-year-old Mohammed Ebrahim Mulla Radhi al-Tooq, as having planted and detonated the bomb that killed the two policemen.

It said Tooq had spent time in Iran and is also suspected of receiving training at a camp operated by Iraq's Hezbollah group.

"Police investigations have found that those arrested had extensive terrorist connections to the Iranian Revolutionary Guards," Bahrain's Chief of Police, Major-General Tariq Al Hasan, said in a statement.

He said forensic tests of the bomb site indicated that the explosives used in the attack consisted of the same substance seized during a foiled attempt to smuggle explosives into Bahrain earlier in July.

"This is yet another disturbing incident in which Iranian actions are attempting to undermine security and stability within Bahrain," he said.

Sporadic violence aimed at Bahraini security forces has become the norm since "Arab Spring" protests led by the Shi'ite community were put down by the government in 2011.

A nuclear deal reached in July between Tehran and global powers has also set its Gulf Arab neighbours on edge, who fear an easing of foreign pressure on Iran due to the deal could embolden it to become more active on their turf.