The aircraft, part of the kingdom's fleet of F-15SAs, "crashed during a training mission", said the statement attributed to defence ministry spokesman Brigadier General Turki al-Maliki, published by the official Saudi Press Agency.

"The accident resulted in the martyrdom of the aircrew," said the statement, without specifying exactly how many died.

An investigation was launched to look into the reasons behind the accident, the statement added.

The incident occurred at 2:28 pm local time (1128 GMT) in the training area of an air base in Khamis Mushait city.

For decades, the F-15 "has been a cornerstone of the relationship" between the Saudi air force and the United States, the Gulf kingdom's main security partner, according to the Defense Security Cooperation Agency, which is part of the US Department of Defense.

"The F-15SA will help deter potential aggressors by increasing Saudi's tactical air force capability to defend against regional threats," the agency said in a 2010 statement notifying the US Congress of the potential sale of 84 such aircraft to Riyadh.

Khamis Mushait is located in Asir province bordering Yemen, where Saudi Arabia has for more than eight years led a military coalition backing the internationally recognised government against Huthi rebels.

The fighting in Yemen has cooled off considerably since a truce was announced in April 2022, even though it officially lapsed in October.