The shooting happened after two boats fishing in the Gulf were pushed off course by waves, say Iranian reports.

Saudi coastguard officers have opened fire on Iranian fishing boats in the Gulf, killing a fisherman, according to Iranian media, amid high tensions between the two rival states.

“Two Iranian boats that were fishing in the waters of the Persian Gulf were pushed off their course by waves. There was shooting by Saudi border guards … and one Iranian fisherman was killed,” the semi-official Tasnim news agency quoted an interior ministry official as saying about Friday night’s incident.

“We are pursuing this matter to determine if the Iranian boats had crossed the Saudi border or not, but the action of the Saudis does not comply with humanitarian and navigational principles,” said Majid Aqababai, an Iranian border affairs official, according to Tasnim.

The IRINN TV news channel also reported the incident, quoting local sources from Bushehr province.

There was no immediate Saudi reaction.

Relations between the two countries are at their worst in years. Last week Riyadh, along with several other countries, severed ties with Qatar, citing its alleged support for “terrorism” and of Iran as reasons. Qatar strongly denied the allegations.

Days later, suicide bombings and shootings in Iran’s capital, Tehran, killed 17 people. After the attack, Shia Muslim Iran repeated accusations that Saudi Arabia funds Sunni fighters, including the Islamic State of Iraq and the Levant (ISIL, also known as ISIS). Riyadh has denied involvement in the attacks.

Iran and Saudi Arabia accuse each other of subverting regional security. They also support opposite sides in conflicts in Syria, Yemen, and Iraq. Iran and Saudi Arabia severed diplomatic ties in 2016.