The Sharif family is now facing two more corruption cases in the accountability court Al-Azizia Steel Mills and Flagship Investments in which they are accused of money laundering, tax evasion and hiding offshore assets. There were no immediate reports of injuries.
Pakistan Tehreek-e-Insaf chairman Imran Khan hit out at Mr Sharif's Pakistan Muslim League Nawaz party, saying those who had gone to greet him at the airport were "donkeys".
Pakistan Muslim League-Nawaz leader Mushahid Hussain Syed on Friday said that the crackdown now underway on political workers in Lahore was being carried out to sabotage the election campaign of his party.
Upon their arrival at Lahore's Allama Iqbal International Airport at 6.15 p.m., both will be arrested and taken to Islamabad by helicopter to be imprisoned at the Rawalpindi Central Jail, Dawn online reported. Four supporters were killed near the election rally of a senior politician from an Islamist party who is running for parliament from the northwestern town of Bannu.
"Why is Lahore under siege?"
No one claimed responsibility for either bombing, but the attacks came days after a suicide bomber dispatched by the Pakistani Taliban killed secular politician Haroon Ahmed Bilour and 20 others at his rally in the northwestern city of Peshawar.
The country's media regulator warned local news channels to abstain from airing statements "by political leadership containing defamatory and derogatory content targeting various state institutions specifically judiciary and armed forces", the regulator said in a statement.
The former prime minister and his daughter Maryam were sentenced to 10 and seven years imprisonment respectively for corruption.
Speaking in a corner meeting, the party chief said that the Pakistan Peoples Party and Pakistan Muslim League-Nawaz harmed the country from their corruption. The party's past five years in power has been punctuated by the civil-military discord that has plagued Pakistan since its inception.
Sharif's PML-N expects a groundswell of support as he returns from London, where his wife Kulsoom is critically ill and undergoing cancer treatment. The military denied the accusations, and said its assistance had been requested by Pakistan's election commission. It plans to place 371,000 soldiers around polling stations so there can a "free and fair" elections, an army spokesman said this week.
In a landmark verdict, the Sharifs were convicted by an anti-corruption court for not being able to prove a legitimate source for funds used to buy a set of upscale London apartments. Sharif was disqualified by the Supreme Court a year ago in the Panama Papers case. They both deny wrongdoing.
After the Supreme Court ousted Sharif last July, the courts barred him from heading the PML-N party he founded. Police have virtually put Lahore on lockdown as scores of Sharif's supporters clashed with police in the evening. His brother Shehbaz became PML-N's president, but Sharif remains the power behind the throne.
The Avenfield corruption case is among the multiple graft cases filed against the former Premier and his children by the anti-corruption body on the Supreme Court's directives in the landmark Panamagate verdict previous year. Many PML-N lawmakers have also defected to Khan's party.
Some cars in the rallies carried plastic or stuffed tigers attached to their rooftops, a nod to the PML-N's election symbol. Sections of the party oppose Sharif's combative approach against the army, and fear it will turn off voters in a deeply conservative and patriotic Muslim nation of 208 million people.