Gurcharan Singh Tohra, Sarb Hind Shiromani Akali Dal chief, suffered a heart attack on Monday night and is stated to be critical.
He has been admitted to the intensive care unit of a hospital in Patiala and hooked on to life support systems.
He suffered the attack within hours of being called to the Akal Takht secretariat by the five high priests for 'discussions' on the proposed merger between his faction of the SAD with that of his rival and former Punjab chief minister Parkash Singh Badal.
