Afghan President Hamid Karzai is considering an offer from international peacekeepers to provide special security troops as bodyguards.

If the need arises, we will look into the option of taking their protection

Tayeb Jawad, Chief of Staff

The offer comes amid a heightened state of alert following the assassination of Vice President Haji Abdul Qadir on Saturday.

The president's chief of staff, Tayeb Jawad, told BBC News Online that an offer of "close protection" had been made by the International Security Assistance Force (Isaf).

But he said that Mr Karzai would continue to be guarded only by Afghans for the time being.

ISAF has stepped up security since the killing of Mr Qadir, deploying extra troops on the streets of Kabul as well as additional helicopter patrols.

Security fears

"There have not been any major changes to Karzai's protection," Mr Jawad said.

Foreign bodyguards could be politically difficult

"If the need arises, we will look into the option of taking their protection," he said.

Some observers say that accepting Isaf bodyguards could dent confidence in Mr Karzai, who is anxious to show that his government is capable of imposing order in the country.

But the BBC's Kate Clark says that most Afghans would not care one way or the other after years of living under warring factions.

Nevertheless, our correspondent says Mr Karzai will probably hesitate before accepting the offer, given the issues of national sovereignty that would arise.

Crime investigation

Isaf has already agreed to join the investigation into Mr Qadir's death, following a request from President Karzai.

Kabul has been on high alert since Qadir's killing

Although 12 people have been arrested for the murder, including 10 security guards, no one has been charged.

There has also been little headway in the investigation into the killing of the minister for civil aviation, who was killed in front of scores of witnesses at Kabul airport five months ago.

According to the Associated Press, members of the team investigating Mr Qadir's death say privately it will be difficult to identify the two gunmen.

"There was no police tape around the scene of the crime," the AP quoted one anonymous Isaf official as saying.

"Some Afghans and news reporters were collecting machine gun casings as souvenirs, or were tramping on shoe steps left over by the assassins," he said.

"That is inadmissible in any serious crime investigation."