Pakistan's three-time Prime Minister Nawaz Sharif arrived home on Saturday from four years of self-imposed exile in London to kick-start his party's campaign three months before a general election, the party said.

The 73-year-old veteran politician will lead a rally in his eastern hometown of Lahore after his chartered plane's arrival in Islamabad with more than 150 people from his party and media organisations, the party and sources said.

Sharif had not set foot in Pakistan since leaving for London in 2019 to receive medical treatment while serving a 14-year prison sentence for corruption. His convictions remain in force, but a court on Thursday barred authorities from arresting him until Tuesday, when he is to appear in court.

While he cannot run again for election or hold public office because of his convictions, his legal team says he plans to appeal and his party says he aims to become prime minister for a fourth time.

Sharif's biggest challenge will be to wrestle back his support base from his main rival, Imran Khan, who despite being in jail remains popular following his ouster from the premiership in 2022.

Khan, too, is disqualified from the elections by virtue of his graft conviction in August, which he has appealed.

Sharif's return comes at a time when the nuclear-armed South Asian nation of 241 million people is experiencing the impact of a worst economic crisis, which was exacerbated during the 16-month rule of his younger brother, Shehbaz Sharif, who led a coalition government after Khan's removal.

The elder Sharif has a record of pursuing economic growth and development. When he was removed as premier in 2017, Pakistan's GDP growth rate was 5.8% and inflation was hovering around just 4%. In September, inflation registered at over 31% year-on-year, and growth is projected to be less than 2% this financial year.

"It is very sad to see that things have deteriorated so badly," Sharif said before boarding the plane in comments telecast by local TV channels.

Rising living costs have become unbearable for many Pakistanis after the younger Sharif's coalition government had to agree to harsh fiscal adjustments to resume funding from International Monetary Fund (IMF), which had suspended payments after Khan scuttled a deal in his last days in office.

Nawaz Sharif has said he was ousted from government at the behest of the powerful military after he fell out with top generals, who play an outsized role in Pakistani politics.

He says the military then backed Khan in the 2018 general election. Khan and the military deny this.

However, the military and Khan fell out in 2022 and over the last few months they have been involved in a bruising showdown, which has afforded Sharif some political space.

The military denies that it interferes in politics.

"An evergreen rule about Pakistani politics is that your chances of taking power are always greater when you're in the good books of the army," said Michael Kugelman, director of the South Asia Institute at the Wilson Center.

"Over his long political career, Sharif's relationship with the military brass has blown hot and cold. It's now in a relatively cordial phase, and he stands to benefit politically."