Pakistan will mark the fifth anniversary of the assassination of former prime minister Benazir Bhutto, with her son expected to launch his political career with a speech in the family's ancestral home town on today.

Bhutto, twice elected prime minister, was killed in a gun and suicide attack after an election rally in Rawalpindi, the headquarters of Pakistan's army, on December 27, 2007. No one has ever been convicted of her murder.

Thousands are expected to gather at the Bhutto family mausoleum at Larkana in the southern province of Sindh and Bilawal Bhutto Zardari, the son of Benazir and of President Asif Ali Zardari, is to make his first major public speech.

The Bhutto family has been a force in Pakistani politics for almost all of the country's 65-year history.

Benazir's father Zulfikar Ali Bhutto led the country from 1971 until he was ousted in a military coup in 1977. He was hanged in 1979 after being convicted of authorising the murder of a political opponent.

With a general election due in the spring, analysts say the ruling Pakistan People's Party (PPP) is eager to introduce a third generation of the dynasty to the public.

"It appears to be the formal launching of Bilawal Bhutto Zardari into politics," political analyst Hasan Askari told AFP.

"Bilawal has symbolic value in the Bhutto family and Zardari would like this link to be used as symbolism in the election."

As head of state President Zardari, who came to power in elections held a month after his wife's murder, is barred from leading the PPP election campaign. He is also hugely unpopular, tainted by years of corruption allegations.

Though the 24-year-old Bilawal will be too young to stand if elections go ahead as expected in the spring -- the lower age limit is 25 -- Askari said he could provide a fresh new figurehead for the PPP campaign.

Bilawal, co-chairman of the PPP with his father, in May accused former military ruler Pervez Musharraf of "murdering" his mother by deliberately sabotaging her security.

A UN report in 2010 also said the murder could have been prevented and accused Musharraf's government of failing to protect Bhutto properly.

The Musharraf regime blamed the assassination on Pakistani Taliban chief Baitullah Mehsud, who denied any involvement and was killed in a US drone attack in August 2009.

There has been a surge in terror attacks in Pakistan in the past weeks. Brigadier Saad Khan, a former officer with the powerful Inter-Services Intelligence agency, warned the Taliban may continue their campaign with an attack on events marking the anniversary.