Pakistan's prime minister-in-waiting and Pakistan Tehreek-e-Insaf (PTI) chief Imran Khan on Thursday condoled former PM Atal Bihar Vajpayee's sad demise.

Khan called Vajpayee a "tall political personality of the subcontinent," news agency ANI reported. 

"His attempts for the betterment of India-Pak relationship will always be remembered," read a tweet posted by PTI's official handle.

"Mr Vajpayee, as a Foreign Minister, took responsibility of improving India-Pak ties," the tweet read. 

"His death has created a void in South Asian politics," PTI said.

South Asian leaders Bangladesh PM Sheikh Hasina and Nepalese Prime Minister KP Sharma Oli also expressed grief on Vajpayee's sad demise.

"He'll be remembered for contributing towards good governance and highlighting issues affecting common people of India as well as regional peace and prosperity," PM Hasina noted.

"Today is a day of great sadness for all of us in Bangladesh," she said.

"I am deeply saddened to learn of the passing away of Shri Atal Bihari Vajpayee, former Prime Minister of India. May the departed soul rest in eternal peace!" tweeted Nepal's Prime Minister KP Sharma Oli.

According to the official statement released by AIIMS, Vajpayee passed away at 5.05pm on Thursday, August 16.

"It is with profound grief that we inform about the sad demise of Former Prime Minister of India, Shri Atal Bihari Vajpayee at 5.05 pm on August 16," the statement noted.

"Shri Vajpayee was admitted in AIIMS on June 11 and was stable in the last 9 weeks under the care of a team of AIIMS doctors. Unfortunately, his condition deteriorated over the last 36 hours and he was put on life support systems. Despite the best efforts, we have lost him today. We join the nation in deeply mourning the great loss," AIIMS stated in the release.