A number of Saudi Arabian Airlines (Saudia) flights have been delayed after the state airline experienced a system failure on Tuesday, just days ahead of Hajj, the annual Islamic pilgrimage which sees millions travel to the holy city of Mecca.

Hajj is expected to take place between August 19 to 24. The mandatory religious journey must be carried out at least once by capable and adult Muslims. It includes the celebration of Eid Al-Adha, which will begin on August 21 and end of August 24 this year.

In a statement issued on Twitter, Saudia informed its guests of flight delays across the network due to “unforeseen system issues”, adding that it is taking all necessary measures to resolve the matter as quickly as possible.

However, it did not reveal how many flights were affected by the failure.

The Hajj has already drawn over 1 million Muslim pilgrims to the kingdom, with another million expected to travel to perform the pilgrimage made to the Kaaba. It is one of Islam’s five pillars.