File photo taken on December 19, 1988 shows the Emir of Qatar, Khalifa bin Hamad al-Thani during his visit to Germany (Photo: AFP)
Qatar began three days of mourning on Monday after the death of former Emir Khalifa bin Hamad Al-Thani, who oversaw the start of the country's transformation into an energy powerhouse.
Prayers were to take place at the national mosque with huge crowds expected, after which the former ruler will be buried. Flags on official buildings flew at half-mast.
Many Qataris took to social media to express their condolences.
A state visit by Venezuelan President Nicolas Maduro was due to go ahead on Monday, but a high-profile conference, involving senior FIFA and Qatar World Cup 2022 officials, scheduled for Tuesday was cancelled as a mark of respect.
However, schools remained open and roads were busy.
The 84-year-old former ruler -- grandfather of the current Emir Tamim bin Hamad Al-Thani -- died on Sunday, Qatar News Agency said, without giving the cause.
Sheikh Tamim ordered three days of official mourning.
Prior to becoming ruler, Khalifa served as Qatar's prime minister and was then a pivotal figure as the tiny emirate established itself as a major global energy producer and subsequently one of the richest countries in the world.
He took power from a cousin in February 1972, just months after Qatar gained independence from Britain.
During his reign the state-owned Qatar Petroleum was set-up in 1974, followed 10 years later by Qatar Gas, now the world's largest liquefied natural gas company.
He was also seen as a founding father of the Gulf Cooperation Council, the political and economic union incorporating the six states in the region.
But while on a private visit to Europe in 1995, Khalifa was deposed in a non-violent palace coup by his son, Sheikh Hamad bin Khalifa Al-Thani, who was defence minister at the time.
One year after his removal, an apparent failed coup was launched in Qatar and 19 people were subsequently charged for trying to return Khalifa to power.
In 2013, Sheikh Hamad handed over to Sheikh Tamim.
The deposed Sheikh Khalifa remained in exile for almost a decade, living in France before returning in 2004 to Qatar where he kept a low profile and was rarely seen in public.
At the time he was deposed, Qatar's population stood at around 490,000 people. Today, it is some 2.6 million, the majority of them foreigners.
The former emir had four wives, five sons and 10 daughters.