Muhammad Adib Mohd Kassim, the firefighter who was severely injured after being attacked by a mob in last month's Seafield temple riots, is back on respiratory support after a deterioration in his condition over the past 24 hours.

In a statement today, the National Heart Institute (IJN) said Adib also continues to require dialysis as his renal function has not improved.

"Adib, in the last 24 hours, had progressive deterioration of his lung function. After thorough assessments, the lungs showed signs of consolidation and hardening of his lung tissue, thus making gas exchange ineffective.

"This is the result of his severe initial lung injury. At the same time, his renal function has not improved, where he continues to require dialysis support. 

"In view of this, and after a multi-discipline team discussion, it was decided to reinsert the Veno-Venous Extracorporeal Membrane Oxygenation (vv-Ecmo) system again at 9pm last night, to assist in his respiratory requirements," read the statement.

Visitation is limited for Adib given his condition.

"Adib is critically ill. We urge all Malaysians to continue praying for his recovery," said IJN.

This comes just five days after Adib's condition was reported as improving.

At the time, IJN said that Adib was taken off the ventilator after showing signs of progress, including being able to communicate with his family and hospital personnel via a whiteboard.