UAE leaders sent condolences to Russian President Vladimir Putin after the death of Moscow's ambassador to the Emirates.
Sergei Kuznetsov, who died suddenly according to reports, served as ambassador since 2019. The cause of death has not yet been released.
On Sunday, President Sheikh Khalifa sent his condolences to Mr Putin.
Sheikh Mohammed bin Rashid, Vice President and Ruler of Dubai, and Sheikh Mohamed bin Zayed, Crown Prince of Abu Dhabi and Deputy Supreme Commander of the Armed Forces, also expressed their sympathies.
The Russian Embassy in the UAE tweeted a tribute.
"The embassy deeply grieves over the death of the Russian Ambassador to the UAE, Sergi Kuznetsov," it said.
The UAE Ministry of Foreign Affairs and International Co-operation also sent condolences.
In a statement published by Emirates news agency Wam, the ministry expressed appreciation for the ambassador’s “tireless efforts to strengthen the bonds of solidarity and friendship between the UAE and Russia during his tenure”, and for helping to promote the strategic partnership between the countries on many fronts in recent years.
Russia and the UAE have worked together in different fields over the years. In 2019, the first Emirati astronaut, Maj Hazza Al Mansouri, was sent to space on board a Russian Soyuz rocket.
Shortly afterwards Mr Putin visited Abu Dhabi, where he met Maj Al Mansouri and the two countries agreed on stronger collaboration in space.
The UAE also took part in the clinical trials of Russia’s Sputnik V coronavirus vaccine.