The son of Pakistan's murdered ex-Prime Minister Benazir Bhutto has promised to fight militancy to maintain democracy, in his first major political speech.
Bilawal Bhutto Zardari told party supporters marking five years since his mother's death that she "sacrificed her life to uphold democracy".
Ms Bhutto died in a gun and bomb attack during her 2007 election campaign.
Her son, whose father is President Asif Ali Zardari, has so far kept a low profile as party chairman.
In remarks carried by Pakistan state television, Mr Bhutto Zardari told a crowd of tens of thousands of Pakistan People's Party (PPP) supporters near his family's shrine in Sindh province that the people were "the source of power".
"The beacon of democracy continues to shine," he said, pledging that his party would fight militancy and extremism to create a peaceful, democratic Pakistan.
The 24-year-old Oxford graduate has been PPP chairman since his mother's assassination, blamed on Taliban militants.
He cannot contest an election until his 25th birthday, which falls next September, some months after a parliamentary vote is due.
It was the first time that Pakistanis had heard Mr Bhutto Zardari speak live on radio and TV and he drew heavily on his family's dynastic role at the heart of the country's politics.
"Bhutto is an emotion, a love," he was quoted as saying, adding that however many Bhuttos were killed, even more would emerge.
Over the next few months, Mr Bhutto Zardari is expected to play a bigger role in party politics, the BBC's Shahzeb Jillani reports from the event in the city of Larkana.
But our correspondent says it will be a while before he emerges from the shadow of President Zardari, who will remain the de facto PPP head and its chief strategist in its bid to return to power next year.
Stressing his family's political legacy, Mr Bhutto Zardari said the party's focus was and would remain on "food, clothes and homes".
Although the PPP government faced considerable challenges from terrorism and a global recession, Pakistan's economy was standing on its own two feet, he said.
President Zardari, who also addressed the crowd, promised that next year's vote would be free and fair and would not be postponed.
Show of strength
Security was tight as activists carrying portraits of Ms Bhutto and her father, former Prime Minister and President Zulfiqar Ali Bhutto, arrived at the shrine. Zulfiqar Ali Bhutto was hanged in 1979, during the military rule of Gen Zia ul-Haq.
The governing PPP is keen to use the rally as a show of strength to demonstrate that despite widespread criticism over its performance during the past five years, it still enjoys popular support, our correspondent says.
Mr Bhutto Zardari's father has been at the forefront of the party until now but faces dwindling support over corruption allegations.
Those fed up with President Zardari's politics are looking to his son to help revive the party's mass appeal, our correspondent says.
The Bhutto dynasty has been a major political force since Pakistan gained independence in 1947.
Ms Bhutto, whose father founded the PPP, was prime minister from 1988 to 1990 and from 1993 to 1996.
On both occasions she was dismissed from office for alleged corruption.
No-one has been charged with her assassination.
A UN inquiry in 2010 found that her murder could have been prevented and that the subsequent investigation was bungled.