Carlos Alcaraz and Jannik Sinner contested last year's Six Kings Slams final, with the winner taking home a reported £4.5m
The Six Kings Slam tennis exhibition event in Saudi Arabia - featuring Grand Slam champions Carlos Alcaraz, Novak Djokovic and Alexander Zverev - has been postponed following a series of deadly attacks on host city Riyadh.
Alcaraz, Djokovic and Zverev were set to travel to the Saudi capital for a three-day event starting on 21 October.
Australia's Alex de Minaur, along with American pair Taylor Fritz and Learner Tien, were also earmarked to play.
The event had been in serious doubt since Yemen's Houthi movement launched attacks on Saudi Arabia at the weekend, including a missile strike on Riyadh's airport on Saturday that killed 13 people and wounded more than 300.
Saudi Arabia's energy minister vowed a "serious" response after the kingdom's oil and gas facilities were also targeted by the Iran-backed Houthis.
Three Saudi Pro League fixtures - including one featuring Cristiano Ronaldo's Al-Nassr - were postponed on Tuesday.
Other future sporting events could be affected by the regional conflict, including Formula 1 races in Qatar and Abu Dhabi.
"The decision reflects Riyadh Season's commitment to delivering sporting events to the highest standards, following an assessment of the organizational and logistical challenges associated with hosting the tournament and their potential impact on the quality of the audience experience," Six Kings Slam organisers told BBC Sport.
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The ANB Arena which hosts the Six Kings Slam is also located in the north of Riyadh, about 31km away from the King Khalid International Airport.
The third edition of the lucrative exhibition, which was won by Italy's Jannik Sinner last year, has been postponed until 27-30 December.
The Saudi Pro League fixture between Al-Riyadh and Al-Hilal, along with Al-Ittihad against Al-Shabab in Jeddah, has also been pushed back until December.
Al-Nassr's trip to Al-Ahli, also based in Jeddah, has been moved to March.
The league cited "logistical considerations" for rescheduling the matches.
On Monday, former Manchester United star Ronaldo scored for Al-Nassr in an AFC Champions League match delayed by an hour because of a missile alert.
In golf, the Asian Tour said it is "closely monitoring the situation in Saudi Arabia" with its season-closing PIF Saudi International scheduled to take place at the Riyadh Golf Club from 18-21 November.
"We are discussing the developing situation with our partner Golf Saudi with respect to hosting the PIF Saudi International in Riyadh in November," the tour told Reuters.
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