April 18 (Reuters) - Egypt's ousted president Hosni Mubarak was taken back to prison from an army hospital on Thursday after appearing fitter at his aborted retrial on charges of complicity in the killings of protesters in 2011.

Hundreds of his supporters blocked the road in front of the hospital late on Wednesday, delaying the transfer, the MENA state news agency said.

"We love you Mubarak" and "Down, down with the rule of the Muslim Brotherhood," chanted the protesters, referring to new President Mohamed Mursi's group.

The retrial of Mubarak will start again on May 11, a Cairo appeals court said on Wednesday. A first attempt collapsed on Saturday when the presiding judge withdrew from the case and referred it to another court.

Judge Mustafa Hassan Abdullah had been widely criticised for acquitting security men accused of attacking protesters in an incident in which crowds were charged at by men riding camels during the 2011 uprising which overthrew Mubarak.

The new presiding judge will be Mahmoud Kamel El-Rashidi, a low-profile jurist.

Many Egyptians were angered when the 84-year-old Mubarak, who was seriously ill last year, appeared in good health, smiling and waving to the public in court on Saturday, and there were calls for him to be sent back to jail.

The prison hospital is fully able to deal with Mubarak's health, the interior minister said in a statement carried by MENA later on Thursday.

Mohamed Ibrahim said that in the event of an "urgent health crises", the former president would be transferred immediately to a hospital outside the prison in accordance with prison regulations.

The prosecutor general's office said it had decided Mubarak would be returned to Torah prison on the outskirts of Cairo. Mubarak was taken by car from the Maadi Military Hospital to the prison in a heavily guarded police convoy early on Thursday, MENA reported. (Reporting by Shaimaa Fayed, Maggie Fick and Ahmed Tolba; Editing by Andrew Roche)