Tennis star has explained a message he wrote on a camera was a tribute to victims of an accident in his home country of Serbia. after a building collapsed in front of Novi Sad railway station in November, with the death toll since rising to 16.

Djokovic wrote a message onto the camera after beating Australian pro Rinky Hijikata at the . It included the number 16, and the veteran would go on to explain the significance.

"I was paying tribute to the 16th victim of a tragedy in our country that happened last year," Djokovic told Tennis Channel (via ). "There were 15 victims, and then unfortunately the 16th happened [on Thursday].

"It's one of the biggest tragedies that we have in our modern history in our country, so it's a sad moment, but in a way, for me to pay respect to the victims." He also paid tribute on social media, writing: "Molitve za 16 žrtava" [Prayers for the 16 victims].

Djokovic, 37, went into the tournament in Miami off the back of a tough few months. He lost to Botic van de Zandschulp in the second round in , but got on track with his straight sets victory over Hijikata.

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The fourth seed followed up that victory with another straight sets win. He triumphed 6-1, 7-6 against Camilo Ugo Carabelli of Argentina in round three, setting up a fourth round meeting with Lorenzo Musetti.

British hopes ended in the second round as Jack Draper was unable to build on , losing to Jakub Mensik. Jacob Fearnley also fell in round two, while Billy Harris and Cam Norrie earlier suffered first-round exits.

Djokovic's victory over Carabelli saw him overtake Rafa Nadal's record for the most Masters 1000 victories. “I’m honoured to have another milestone, another record broken,” the Serb said after passing his long-time rival's total. “There’s always something on the line pretty much every time I play, and of course that motivates me to do well at tournaments.”

Fourth round opponent Musetti has been forced to twice come from behind already in the tournament. The 15th-seeded Italian beat Quentin Halys in round two after holding his nerve in a second set tie-break, before winning 4-6, 6-2, 6-3 against Canada's Felix Auger-Aliassime.

Jannik Sinner is the reigning champion in Miami, but is unable to defend his title after . The 23-year-old is due back in action in early May, and will have a chance to compete at Roland Garros and Wimbledon in an effort to add to his Australian Open and US Open crowns.