Pakistani nuclear scientist Abdul Qadeer Khan died on Sunday morning in Islamabad, Dawn reported. He was 85.

Known as the “father of Pakistan’s nuclear bomb”, Khan had contributed to the establishment of the country’s first nuclear enrichment plant, according to the BBC.

Khan was also infamous for allegedly passing on nuclear secrets to countries like North Korea and Iran, the BBC reported. He had been arrested in 2004.

Pervez Musharraf, who was then the president of Pakistan, had pardoned Khan, AFP reported. After that, Khan was placed under house arrest for five years.

Despite the accusations, Khan was celebrated as a national hero in Pakistan.

The scientist had tested positive for Covid-19 in August this year, according to AFP. He was admitted to the Khan Research Laboratories Hospital in Islamabad and was discharged after he recovered, according to Dawn.

But late on Saturday, Khan’s health worsened, Geo News reported. He was taken to the same hospital. He died at 7.04 am on Sunday.

Pakistan Prime Minister Imran Khan and President Arif Alvi took to Twitter to pay tributes to the scientist.

“Deeply saddened by the passing of Dr AQ Khan,” Imran Khan said. “He was loved by our nation because of his critical contribution in making us a nuclear weapon state. For the people of Pakistan he was a national icon.”

Alvi tweeted: “He helped us develop nation-saving nuclear deterrence, and a grateful nation will never forget his services in this regard.”

The scientist was given a state funeral in Islamabad, according to Dawn. Members of the Pakistani Cabinet and military officers attended the event.