The first group of Iranian pilgrims heading for Mecca boarded a plane at Tehran’s Imam Khomeini airport on Monday, after Tehran boycotted the pilgrimage in 2016 amid tensions with Saudi Arabia.

Nearly 90,000 Iranians are expected to attend the hajj in Mecca this year.

Iran boycotted the hajj in 2016 after hundreds of people, many of them Iranians, died in a crush at the pilgrimage in Saudi Arabia in 2015, and following a diplomatic rift between the two countries who are vying for power and influence in the region.

In a speech to hajj organizers on Sunday, Iranian Supreme Leader Ayatollah Ali Khamenei said that Iranians would never forget the “catastrophic events” of 2015 and called on Saudi Arabia to ensure the security of all pilgrims.

Riyadh severed diplomatic relations in 2016 after Iranian protesters stormed the Saudi embassy in Tehran following the execution of a Shi’ite cleric in Saudi Arabia in January 2016.

In February 2017, which is predominantly Shi’ite Muslim, sent a delegation to Saudi Arabia, which is mostly Sunni, that initiated the process of Iranian pilgrims returning for the hajj.