The United Arab Emirates’ long-ailing ruler, Sheikh Khalifa bin Zayed Al Nahyan, died Friday, the government’s state-run news agency announced in a brief statement. He was 73.

The UAE’s Ministry of Presidential Affairs announced a 40-day period of mourning and a three-day suspension of work in all ministries and the private sector beginning Friday, including flags to be flown at half-staff, according to the Associated Press.

He had long ceased having involvement in day-to-day affairs of ruling the country, with his brother, Abu Dhabi’s Crown Prince Mohammed bin Zayed, seen as the de-factor ruler. There was no immediate announcement about a successor, although Mohammed bin Zayed is in line to inherit the top post.

Sheikh Khalifa, who has rarely been seen in official photos or at public events for years, succeeded his father and the UAE’s founder Sheikh Zayed in 2004. He suffered a stroke a decade later, keeping him largely out of public sight ever since.

The world’s tallest tower in the UAE’s emirate of Dubai is named the Burj Khalifa after the late ruler, whose oil-rich emirate helped bail Dubai out during a financial crisis.