BEIRUT, Lebanon — Sultan Qaboos bin Said of Oman, who over nearly five decades in power transformed his Persian Gulf kingdom from an isolated enclave into a developed nation known for brokering quiet talks between global foes, has died, the Omani government announced on Saturday. He was 79.

His death was announced by the official Oman News Agency. The announcement did not mention the cause, but Qaboos had been receiving treatment in Europe for cancer since at least 2014.

Qaboos’s decades as an absolute monarch who used oil wealth to pull his country from poverty made him a towering figure at home, with roads, a port, a university, a sports stadium and other facilities bearing his name. Internationally, as the longest-serving leader in the Arab world, he used Oman’s place in a turbulent region, next to one of the world’s busiest shipping lanes, to become a discreet but essential diplomatic player.

In a region rife with sectarianism, political divides and foreign interference, the soft-spoken, diminutive Qaboos championed a foreign policy of independence and nonalignment. He became a rare leader who maintained ties with a wide range of powers that hated one another, including Iran, Israel, the United States, Saudi Arabia and the Houthi rebels in Yemen.