Abdul Qadeer Khan, the scientist who turned Pakistan into nuclear power and subsequently sold its nuclear secrets, died on Sunday after contracting Covid-19. He was 85 years old at the time.

According to state-run television PTV, Khan was admitted to the Khan Research Laboratories Hospital with respiratory issues on August 26 after testing positive for the coronavirus.

According to accounts, he was later transferred to a military hospital in Rawalpindi.

President Arif Alvi of Pakistan remarked in a tweet that he was "deeply saddened" to learn of the death of Dr. Abdul Qadeer Khan, whom he had known since 1982.

"He contributed to the development of nation-saving nuclear deterrence, and a grateful nation will never forget his contributions."

Khan was praised for bringing Pakistan's nuclear defenses up to par with arch-rival India's and making them "impregnable."

In 2004, he was at the center of a global nuclear proliferation controversy involving selling nuclear secrets to North Korea, Iran, and Libya. After confessing on national television, Khan was pardoned by then-President Pervez Musharraf, but he remained under house detention in his opulent Islamabad mansion for years.

Khan was diagnosed with prostate cancer in 2006, but he recovered following surgery.

Khan's house detention was lifted in February 2009, but his movements were closely monitored, and he was accompanied by police whenever he left his home.

Khan admitted that he acted alone, without the knowledge of state leaders, in his confession. He later claimed, however, that he had been used as a scapegoat.