Kulsoom, who was under treatment at London's Harley Street Clinic since June 2014, was placed on life support earlier Tuesday after her health deteriorated, Geo TV reported.

The health of the 68-year-old former first lady began deteriorating Monday night as she had developed a lung problem again, the channel said.

Sharif's brother and Pakistan Muslim League-Nawaz president Shehbaz Sharif confirmed her death in a tweet.

"My sister-in-law and the wife of Nawaz Sharif sahib is no more amongst us. May God bless her soul," he tweeted in Urdu.

Nawaz Sharif, his daughter Maryam and son-in-law Captain (retd) Muhammad Safdar are currently serving jail terms in Adiala Jail in Rawalpindi after being convicted by an accountability court in a corruption case in July.

Citing sources, the channel said Sharif, Maryam, and Safdar have been informed about Kulsoom's death.

According to sources, the Sharif family has decided to bring back Kulsoom's body to Pakistan, it said.

"She will be laid to rest in Pakistan," the family confirmed.

Prime Minister Imran Khan has condoled the death of Kulsoom.

In a statement, the prime minister said all facilities will be provided to the family and heirs of Kulsoom as per law.

The prime minister has directed the Pakistan High Commission in London to assist in provision of all necessary facilities to the family of the deceased, the statement said.

Army Chief Gen. Qamar Jawed Bajwa also expressed grief over Kulsoom's death and extended condolences to her family.

"COAS expresses his grief and heartfelt condolences to the bereaved family on sad demise of Begum Kulsoom Nawaz," the army spokesperson tweeted.

The former first lady was diagnosed with lymphoma (throat) cancer in August last and had been in London since, where she underwent multiple surgeries and at least five chemotherapy sessions.

She was placed on a ventilator in June following a cardiac arrest. Her family reported a slight improvement in her condition on July 12, a day before her husband Sharif and Maryam were set to return to Pakistan after the accountability court sentenced them to jail.

She served as the first lady of Pakistan for three non-consecutive terms from 1990-1993, 1997-1999 and 2013-2017.

She also served as the president of the PML-N from 1999 to 2002, after her husband's government was toppled by former military dictator Pervez Musharraf in a bloodless coup. She was also placed under house arrest following Sharif's ouster by Musharraf in 1999.

Kulsoom was elected to Lahore's NA-120 constituency in a by-poll after her husband was disqualified from the seat by the Supreme Court last year. Due to her illness, she was unable to return and formally take oath for the seat.

She was born in 1950 in Lahore to a Kashmiri family. She graduated from the Forman Christian College in Lahore and received a Master's degree in Urdu from Punjab University in 1970.

From her maternal side, she was granddaughter of famous wrestler of the sub-continent Gama Pehlwan.

Kulsoom married Sharif in April 1971.

She is survived by her husband and four children - Hassan, Hussain, Maryam and Asma.