“His Highness Sheikh Khalifa Bin Zayed Al Nahyan, President of the United Arab Emirates and Ruler of Abu Dhabi has passed away. As a mark of respect to the departed dignitary, the Government of India has decided that there will be one day’s state mourning tomorrow throughout India," said Union home ministry in a statement.
The national flag will be flown at half-mast on all buildings where it is flown regularly and there will be no official entertainment.
The UAE's President Sheikh Khalifa bin Zayed Al-Nahyan died on Friday aged 73 after a years-long battle with illness, triggering a period of mourning and a handover of power in the oil-rich Gulf state.
Sheikh Khalifa, who was in office during a time of rocketing fortunes for the UAE but was rarely seen in public, is likely to be replaced by his half-brother, Abu Dhabi Crown Prince Mohammed bin Zayed, who was already viewed as the country's de facto ruler.
The most visible testament to Sheikh Khalifa is the world's tallest building, Dubai's Burj Khalifa, which was renamed after he bailed out the debt-hit emirate when the global financial crisis struck in 2009.
UAE has announced 40 days of mourning, with flags at half-mast from Friday and work suspended in the public and private sectors for the first three days.
Funeral prayers were set to take place later on Friday.
As condolences poured in from abroad, US President Joe Biden called Sheikh Khalifa "a true partner and friend of the United States".
Lebanon, Kuwait and neighbouring Oman also ordered three days of mourning.
Sheikh Khalifa took over as the UAE's second president in November 2004, succeeding his father as the 16th ruler of Abu Dhabi, the richest of the federation's seven emirates.
