Tunisian President Beji Caid Essebsi has died, government officials said, after he was hospitalised with a severe illness in late June.

Essebsi, 92, who was the oldest head of state after the Queen, returned to intensive care on Thursday, his son said, reviving fears of a power vacuum ahead of November polls.

Things are not going well", Hafedh Caid Essebsi told AFP earlier on Thursday.

Essebsi appeared feeble in a video released by his office on Monday of a meeting at the defence ministry.

Concerned for the country's stability, politicians and social media users have called for greater transparency about the president's health since he was hospitalised last month.

Essebsi, the country's first democratically elected president, came to power in 2014, three years after the Arab Spring uprising toppled longtime despot Zine El Abidine Ben Ali and sparked revolts in several Arab nations.

A veteran politician, Essebsi served as an adviser to Habib Bourguiba, the father of Tunisia's independence from France, holding a number of key jobs under him and later under Ben Ali.

Over the years, Essebsi was director general of the national police and interior minister. He later held the defence portfolio before becoming ambassador to France.

He became prime minister after the 2011 uprising and organised parliamentary elections later that year.