Afghan President Hamid Karzai on Friday vowed to persevere with efforts to broker peace with the Taliban as he led thousands of mourners at the funeral of his assassinated peace envoy Burhanuddin Rabbani.

Kabul police deployed thousands of extra officers as part of a security lockdown designed to protect the funeral prayers at the presidential palace and the burial site from increasingly brazen gun and suicide attacks.

But the anger of Rabbani's supporters spilled over as they threw stones at government officials' vehicles at the burial scene and chanted: "Death to America, death to Pakistan (blamed by some for the killing), death to Karzai".

The crowd was quickly dispersed when officials' guards fired warning shots in the air but the incident highlighted ethnic tensions following the death of Rabbani, a key Tajik ally of the Pashtun Karzai.

Rabbani, who was president during the 1992-1996 civil war, before becoming chairman of Karzai's hand-picked High Peace Council, was killed on Tuesday by a turban bomber purporting to be a peace emissary from the Taliban leadership.

He was the most senior national leader assassinated in Afghanistan since the 2001 American invasion.

Following the killing of Karzai's brother Ahmed Wali Karzai, his kingpin in the south, and last week's 19-hour siege of the US embassy, the government has never seemed weaker in the face of the 10-year Taliban insurgency.

In a speech as Rabbani's body lay in state at the presidential palace, Karzai insisted that the murder would not derail efforts to make contacts with insurgents, despite keeping up the fight.

"The blood of the martyred (Rabbani) and other martyrs of freedom requires us to continue our efforts until we reach peace and stability," Karzai said.

"We will continue our efforts to reach peace which was the wish of martyred ustad (professor) but at the same time time, we consider it as our responsibility to fight the enemies of peace with determination."

Hundreds of Afghan dignitaries and foreign ambassadors earlier filed past the coffin, draped in the Afghan flag and covered in flowers, at the palace.

The body was buried on top of a hill overlooking the Afghan capital where hundreds of ordinary Afghans carrying pictures of Rabbani and banners had gathered to witness the burial, and where the angry scenes broke out.

Mourners vowed to avenge Tuesday's death of Rabbani, a prominent warlord in the fight to evict Soviet troops from Afghanistan in the 1980s who had a strong powerbase in the Tajik north.

Enayatullah, a Tajik university student, said: "We are all grieving, people here have lost a great leader."

"We vow to take the revenge for Burhanuddin Rabbani. We also demand that the government detain those behind the killing of Rabbani."

"We want those who organised this meeting (Rabbani's ultimately fatal meeting with the turban bomber) to be put on trial, even if they are members of the High Peace Council."

Police said thousands of extra officers were being deployed 'on the highest state of alert' for the funeral, with the army and intelligence service also on standby.

"We have taken extra measures by deploying thousands of policemen, over 3,000, especially for the funeral," the head of Kabul's criminal investigations unit, Mohammad Zahir, told AFP.

Police, some in armoured vehicles, and intelligence agents lined the streets while a large security cordon was in place in the area near Rabbani's home from which cars were banned and where pedestrians were being searched.

Karzai has said the assassin gained access to the 71-year-old Rabbani by bringing a CD with an apparent 'message of peace' from the Taliban.

The attacker apparently waited four days for Rabbani to return from an overseas trip before detonating his explosives as the pair hugged in greeting.

Unusually, the Taliban have so far refused to comment on Rabbani's killing, but Afghan police and intelligence officials have blamed the militia.

Afghanistan's spy agency, the National Directorate of Security, said it believes the Taliban's leadership body, the so-called Quetta Shura, was involved in the killing but has given no further details.

The Taliban are leading an insurgency against Karzai's government and the 140,000 foreign troops stationed in Afghanistan who support it.