Manama, Asharq Al-Awsat—Bahraini authorities arrested several people on Wednesday, in connection with a terrorist attack which took place on Tuesday and was the deadliest bombing in the country since March 2014, the Bahrain News Agency reported.

The attack took place outside a girls’ school in the eastern village of Sitra, killing two policemen and wounding six other people.

Prime Minister Prince Khalifa Bin Salman Al Khalifa said that “foreign elements” were behind the attack, but did not name any specific country. He added that Bahrain “categorically rejected any foreign interference” on its soil.

This comes as authorities said on Saturday they had foiled a plot by Iranian-linked operatives to smuggle explosives into the country. Bahrain’s Interior Ministry on Wednesday said Tuesday’s attack used the same kind of explosives as those recovered by authorities on Saturday.

Tehran, meanwhile, dismissed suggestions it was connected to both Tuesday’s bombing and those arrested on Saturday. Iran’s Foreign Ministry dismissed the allegations as “state media propaganda” and condemned the bombing.

“Terrorism and extremism are the main challenges facing the region,” Iranian Foreign Ministry spokeswoman Marzieh Afkham was quoted as saying by Iran’s Press TV.

A security source told Asharq Al Awsat an unknown group called the Islamic Resistance Brigades to God announced their responsibility for the Sitra attack. The source added that “Bahraini security has taken the group’s statement very seriously and will increase security measures” in response.

The attack drew strong condemnations from fellow Gulf Arab states, especially from Saudi Arabia, which like Bahrain accuses Iran of seeking to foment instability in Arab countries.

Bahrain has long accused Iran of stirring up unrest among its population and tensions between the two countries have risen in recent days, with Bahrain recalling the Iranian ambassador following Saturday’s arrests.