Rahim Al-Hussaini was named Wednesday as the new Aga Khan, spiritual leader of the world’s millions of Ismaili Muslims.

He was designated as the Aga Khan V, the 50th hereditary imam of the Shiite Ismaili Muslims, in his father’s will. His father died Tuesday in Portugal.

The Aga Khan is considered by his followers to be a direct descendant of the Prophet Muhammad and is treated as a head of state.

The Aga Khan Development Network and the Ismaili religious community announced earlier that His Highness Prince Karim Al-Hussaini, the Aga Khan IV and 49th hereditary imam of the Shiite Ismaili Muslims, died surrounded by his family.

It said his burial and will-reading will be held in the coming days, followed by an homage ceremony.

The late Aga Khan was given the title of “His Highness” by Queen Elizabeth in July 1957, two weeks after his grandfather the Aga Khan III unexpectedly made him heir to the family’s 1,300-year dynasty as leader of the Ismaili Muslim sect.

A defender of Islamic culture and values, he was widely regarded as a builder of bridges between Muslim societies and the West despite — or perhaps because of — his reticence to become involved in politics.

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The Aga Khan Development Network, his main philanthropic organization, deals mainly with issues of health care, housing, education and rural economic development. It says it works in over 30 countries and has an annual budget of about $1 billion for nonprofit development activities.

Ismailis lived for many generations in Iran, Syria and South Asia before also settling in east Africa, Central Asia and the Middle East, as well as Europe, North America and Australia more recently. They consider it a duty to tithe up to 12.5% of their income to the Aga Khan as steward.