The PM has been rallying crowds since Wednesday as he makes his way down the major road from capital Islamabad to his party's stronghold in the eastern city of Lahore.
The ex-leader has been rallying crowds since Wednesday as he makes his way down the major road from capital Islamabad to his party's stronghold in the eastern city of Lahore, weeks after he was deposed by the Supreme Court.
"A 13-year-old boy who had came to see the rally was hit by a car in the convoy," Sajid Ali, head of the local Lalamusa police station, told AFP.
An investigation had been launched, he said.
Railways minister Khawaja Saad Rafique called the teenager "the first martyr of this movement for democracy" in an address to the thousands-strong crowd in nearby Gujrat.
One of the vehicles in the motorcade hit and killed the boy as he crossed a divider on the road, the minister said.
Sharif said in his Gujrat speech he would personally visit the boy's home "and try to help his family for life".
As at previous stops along the route, Sharif railed against the court's decision, insisting his conscience was "clean" against allegations of corruption.
Supporters chanted "prime minister Nawaz Sharif" and danced to songs praising his party as the former leader addressed the crowd from a makeshift stage behind bulletproof glass.
Thousands had turned out to catch a glimpse of Sharif as his convoy rolled down the Grand Trunk Road, a more than 2,000-year-old trade route which leads from Chittagong in Bangladesh across India and Pakistan to the Afghan capital Kabul.
Sharif hopes to bring tens of thousands more into the streets in Lahore but it is not yet known when he will arrive in the Punjabi capital.
He is travelling in a bomb-proof vehicle especially designed for the journey.
The convoy is surrounded by heavy security, with fears lingering after a truck bomb exploded in Lahore on Monday, killing one person and injuring dozens.
Supporters gathered in Gujrat voiced frustration over the ex-prime minister's ouster.
Umair Mazhar, 26, insisted no allegations of corruption had been proven against the former leader.
"The Supreme Court should do justice to Sharif and restore him," he told AFP.
Sharif was the 15th prime minister in Pakistan's 70-year history -- roughly half of which has been spent under military rule -- to be ousted before completing a full term.
The top court sacked him last month after an investigation into corruption allegations against him and his family, briefly plunging the nuclear-armed nation into political uncertainty.
Within days of Sharif's ouster the PML-N nominated former oil minister Shahid Khaqan Abbasi as a new prime minister, with the National Assembly rubber-stamping their choice.
He was originally seen a placeholder for Sharif's younger brother, Shahbaz, who is chief minister of Punjab.
But reports this week said the party appeared to be backtracking on the succession plans announced by Sharif, saying the PML-N would likely keep Abbasi in place until next year's general elections.
On Friday a party official told AFP Sharif's wife would contest the parliamentary seat left vacant after his removal.
Until now Begum Kulsoom Nawaz Kulsoom, who has been married to Sharif for 46 years, has largely stayed out of politics.