BEIRUT (Reuters) - Iran’s Revolutionary Guards have detained a Saudi Arabian fishing boat and arrested its crew, an Iranian state news agency reported on Saturday, at a time of increased diplomatic tension between the two regional powers.

Five Indian nationals on the vessel were detained on Friday after they crossed into Iranian territorial waters in the Gulf, Ardeshir Yarahmadi, a spokesman for the fisheries department of Bushehr province, was quoted as saying by the Islamic Republic News Agency (IRNA).

Yarahmadi said it was the second time in the past month that a Saudi boat and its crew had been detained.

Relations between Iran and Saudi Arabia are at their worst in years, with each accusing the other of subverting regional security and supporting opposite sides in conflicts in Syria, Iraq and Yemen.

Riyadh, along with other Arab governments, has severed ties with Qatar, citing its support of Iran as one of the main reasons for the move.

Iran has blamed Saudi Arabia for being behind deadly twin attacks on June 7 in Tehran claimed by Islamic State. At least 18 people were killed and more than 40 wounded in the attacks, in which Riyadh has denied any involvement.

Iranian media reported last month that Saudi border guards had opened fire on Iranian fishing boats in the Gulf, killing a fisherman and arresting three others.

Iran has urged Saudi Arabia to release the trio, who Tehran said had legal documents but lost their way.

The Saudi Information Ministry said it had intercepted the boat in Saudi waters on June 16 and that three members of Iran’s elite Revolutionary Guards had been detained in the incident.

It said the seized vessel was carrying explosives and those captured intended to conduct a “terrorist act” in Saudi territorial waters. Iran has denied the allegation.