The UAE's long-time de facto ruler Sheikh Mohamed bin Zayed Al Nahyan was elected as president on Saturday, official media said, a day after the death of former leader Sheikh Khalifa.

Sheikh Mohamed was elected by the Federal Supreme Council, WAM news agency said, becoming the ruler of the oil-rich country founded by his father in 1971.

Sheikh Mohamed, often known as 'MBZ', met members of the Federal Supreme Council, made up of rulers of the UAE's seven emirates, as the oil-rich country enters a period of mourning for his half-brother Sheikh Khalifa.

His ascension, which was widely expected, formalises his position as leader of the desert state of 10 million after years of calling the shots while Sheikh Khalifa was sidelined by poor health.

Under his low-key direction, the United Arab Emirates has put a man in space, sent a probe to Mars and opened its first nuclear reactor, while using its oil-funded clout to develop a more assertive foreign policy.

Closely allied with Saudi Arabia, it has emerged as a leader of a reshaped Middle East since the retreat of traditional powers and the reduced involvement of the United States, forging ties with Israel and joining a war against Iran-backed militants in Yemen.