Supporters of Pakistani opposition politician Imran Khan celebrate a court ruling against Sharif this month. (AP: K.M. Chaudary)
The attack happened as the former prime minister returned to Lahore, where police arrested scores of his Pakistan Muslim League party workers to prevent them from greeting him at the airport.
In a video message on Friday reportedly from aboard his aircraft en route to Pakistan, Sharif said he was returning knowing he would be taken directly to prison.
Sharif has been banned from participating in politics, and his brother Shahbaz Sharif now heads his Pakistan Muslim League and is campaigning for re-election on July 25.
In a televised appeal to supporters from London earlier this week, Sharif said he was not afraid of prison and asked people to vote for his party.
He also used the opportunity to again criticise Pakistan’s powerful military, which has ruled the country directly or indirectly for most of its 71-year history, saying Pakistan now has a “state above the state”.
During his term in office, Sharif criticised the military’s involvement in civilian affairs and its efforts in fighting extremists.
Pakistani and international rights groups have accused the military of seeking to maintain its influence in Pakistani politics by keeping Sharif out of power.
Sharif’s supporters protest the 10-year prison sentence. (AP: B.K. Bangash)
The military denied the accusations, saying their assistance in carrying out the elections was requested by Pakistan’s election commission. The army will deploy 350,000 security personnel to polling stations throughout the country on election day.