Saudi Arabia on Thursday denied allegations it had completed a probe into an attack on its missions in Iran, the country’s official news agency reported.

Axar.az reports citing on Anadolu agency that. the probe is still being carried out into last year’s attack on Saudi diplomatic missions in Tehran and Mashhad province, the SPA News Agency reported.

Iran denied a Saudi delegation visas to obtain onsite information for the probe, said the report, citing a statement from an official source at the Ministry of Foreign Affairs.

Tensions have mounted between Saudi Arabia and Iran since Riyadh cut diplomatic ties with Tehran after the diplomatic missions were attacked in January last year by Iranian protesters.

The attacks were prompted by Saudi Arabia’s decision to execute prominent Shia cleric Nimr Baqir al-Nimr, who was among 47 people executed Jan. 2, 2016, for terrorism offenses.

Saudi Arabia and its Gulf allies also accuse Tehran of arming and supporting Yemen’s Shia Houthi group that overran the Yemeni capital Sanaa and other parts of the country in 2014.

The six-year-old conflict in Syria has also contributed to the deterioration of Arab-Iranian relations.

While Shia Iran is a close ally of the regime of Syria's Bashar al-Assad, Saudi Arabia is a primary backer of Syria’s anti-regime armed opposition