Agencies contributed to this report.
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Haftar is seen walking around the Kaaba in white pilgrimmage robes surrounded by guards in military uniform in a video on Tuesday shared widely on Twitter.
Performing the Umrah in Ramadan has a major significance in Islam, equivalent to performing the Hajj in the company of the prophet, according to Islamic tradition, and is said to earn forgiveness for all sins.
As Haftar's forces have been accused of war crimes, Libyans and Arabs on social media expressed outrage both at Saudi Arabia's hosting of the warlord and his attempt to exploit religion to polish is image.
"Haftar circumambulates the Kaaba as his Emirati planes circle over Tripoli," said one Twitter user as many expressed outrage.
The United Arab Emirates, along with Saudi Arabia and Egypt, is seen as a key supporter of Haftar and has provided his Libyan National Army (LNA) with aircraft and military vehicles.
Haftar travelled to Cairo on Thursday to discuss the situation in Libya with Egyptian President Abdel Fattah al-Sisi.
The Gaddafi-era general, whose forces hold the east of the country, launched an offensive on April 4 to seize Tripoli where the internationally recognised Government of National Accord (GNA) is based.
Fayez al-Sarraj, head of the GNA, travelled to Europe last week seeking support from Europe against Haftar.
Last month, Libya's controversial grand mufti called on Muslims to boycott travelling to Saudi Arabia for the Hajj and Umrah pilgrimages.Hundreds have been killed in the fighting and thousands wounded, according to the World Health Organisation.
He said the money paid to Saudi Arabia in order to go on either pilgrimage would "help Saudi Arabian rulers to carry out crimes against our fellow Muslims".
Ghariani, who issued a fatwa calling for jihad against Libya's former dictator Muammar al-Gaddafi in 2011, has made his opposition to Haftar well known.
Libya has been mired in chaos since the ouster and killing of Gaddafi, with Haftar supporting a rival administration in the east of the country.