A top Afghan official has said the assassination of Vice-President Haji Abdul Qadir underlines the need to disarm the country's powerful rival factions.

Everybody in Afghanistan would like to see the armed groups being disarmed

Tayyeb Jawad Afghan president's chief of staff

Tayyeb Jawad, chief of staff of President Hamid Karzai, told the BBC that the new government needed to assert central control.

Two arrests have been announced following the killing of Qadir, who was buried in his home city of Jalalabad with full military honours on Sunday.

Two unidentified gunmen shot and killed him along with his driver outside government buildings in Kabul on Friday.

Mr Jawad said the government was considering asking international Isaf peacekeepers to help in the investigation.

"Everybody in Afghanistan would like to see the armed groups being disarmed and a general demobilisation taking place," he said.

Afghanistan is awash with weapons and munitions after decades of war.

He drew a distinction between armed groups under the command of the central government and those who did "not obey the laws of Afghanistan".

Asked what plans the government had to disarm the groups, he said a commission had been formed but it would be a "gradual process".

Arrests

Afghan TV reports that two men have been arrested trying to leave Kabul in a car like the one used by Qadir's killers to escape.

The two men have been handed over to the special commission investigating the killings.

In the immediate aftermath of the attack, 10 guards on duty at the Ministry of Works where Qadir was killed were arrested for failing to react properly, local police said.

Pashtun voice

Qadir was, along with Mr Karzai, one of the few members of Afghanistan's dominant Pashtun community to have a prominent post in the government.

Qadir was a rare Pashtun voice in the government

The BBC's Rahimullah Yusufzai reports that, in the wake of the killing, Pashtun leaders have renewed demands for the ethnic make-up of the government to resemble more closely that of the country.

They want more Pashtuns instead of the current Tajik monopoly - a cause also promoted by Qadir.

Qadir, who will be remembered by national mourning on Tuesday, was an influential figure in the country's mainly Pashtun eastern provinces.

US concern

President Karzai has admitted his security forces may lack the "professional skills and equipment" needed to catch the killers and may turn to foreign organisations for help.

The US already has 7,000 troops in Afghanistan

President George W Bush said after the killing that the US should step up work to train the nascent Afghan army but he faces calls at home to give greater direct military support.

For Senator Chuck Hagel, who serves on the Senate Foreign Relations Committee, US prestige is at stake.

"I fear that we may see this government and our efforts unwind here if we don't make the appropriate investment of men and effort and resources," he said.

"If we lose there, if this goes backward, this will be a huge defeat for us symbolically in that region, in the world."