Ousted Pakistani leader Nawaz Sharif is returning to Pakistan despite facing a 10-year jail sentence for corruption.
Sharif and his daughter Maryam face arrest when they arrive in Lahore from the UK later on Friday.
The three-term PM was ousted from office last year after a corruption investigation. He was sentenced in absentia to 10 years last week.
He has accused Pakistan's powerful security establishment of conspiring against him ahead of 25 July elections.
"There was a time when we used to say a state within a state, now it's a state above the state," he told supporters of his Pakistan Muslim League-Nawaz (PML-N) party in London earlier this week.
PML-N supporters are expected to flock to Lahore airport to greet Mr Sharif, who was convicted by an anti-corruption court last week over his family's ownership of four luxury flats in London.
Thousands of police officers have been deployed and shipping containers have been placed on some main roads to block supporters from reaching the airport.
On Thursday, the PML-N said hundreds of party activists in Lahore had been detained ahead of Sharif's return. He has called for a "mass gathering of the people".
Speaking to the BBC at Abu Dhabi airport as he waited to change planes on Friday, he said: "What credibility will these elections have when the government is taking such drastic action against our people and this crackdown is taking place all over the country?"
Why is Sharif returning?
He says he is doing it for the people of Pakistan, which is at a "critical juncture" ahead of the elections.
But the BBC's M Ilyas Khan in Islamabad says he also needs to surrender to the National Accountability Bureau (NAB) court which convicted him to file an appeal, and then apply for bail.
He may also be contemplating protests after the election, in which he is disqualified from running.
He is expected to land in Lahore on an Etihad Airways flight from London, via Abu Dhabi.
Why does he blame the military?
Sharif, 67, has been one of the country's leading politicians for most of the past 30 years. He remains popular, especially in Punjab, the most populous and electorally significant province.
He and his party have accused the military of being behind his conviction, saying it is going after the PML-N for its criticism of the security establishment and the party's policy to improve ties with India.
In May, the Dawn newspaper published an interview in which Sharif questioned the wisdom of "allowing" Pakistani militants to cross the border and kill 150 people in Mumbai, referring to attacks in the Indian city in 2008.
The military, which has ruled Pakistan for about half of its 70-year history, has denied it has any "direct role" in the elections or the political process.
Sharif walks into a jail cell
Analysis by the BBC's M Ilyas Khan in Islamabad
The last time Nawaz Sharif was sentenced to a jail term after a military coup in 1999, he chose to accept a pardon and exile under a Saudi-brokered deal. But this time, he is walking into a jail cell.
Back then, it was thought that being the spoilt son of a wealthy father, he was too soft to face the various hardships that can befall a Pakistani politician.
But his moves this time underline that he is willing to traverse tougher territory.
Sharif may well be contemplating wider protests after the election, which many believe the military has already "engineered" enough to ensure his party doesn't win.
And he may have made a huge personal sacrifice for this. Sharif has left behind his wife Kulsoom, who has cancer, on life support in a London hospital, knowing that he may not be able to return to be by her side.
What was he found guilty of?
Last week the NAB court ordered Sharif to serve 10 years for owning assets beyond his income and one year for not co-operating with the NAB. The sentences are to be served concurrently.
His daughter, Maryam Nawaz Sharif, received seven years for abetting a crime and one year for not co-operating - again to run concurrently - while son-in-law Safdar Awan was given a one-year sentence for not co-operating.
Sharif and Maryam also received fines of £8m ($10.6m) and £2m respectively.
The case, known as the Avenfield Reference, relates to a number of properties in the UK capital.
The Panama Papers leak in 2015 revealed several of Sharif's children had links to offshore companies, which were allegedly used to channel funds and buy foreign assets - including luxury flats in Avenfield House, on London's Park Lane.
His family, however, insist they legitimately acquired the four properties.
Pakistan's general election
- Voters will elect candidates for the 342-seat Pakistan National Assembly
- The main parties are Nawaz Sharif's PML-N, former cricketer Imran Khan's PTI and Bilawal Bhutto Zardari's PPP
- It will mark the second time that one civilian government has handed power to another after serving a full term
- The run-up to the vote has been marred by what observers say is a crackdown on political activists, journalists and critics of the powerful military
- More than 371,000 troops will be deployed to protect the election and ensure it is "free and fair", the army says