The measures were imposed by the UN Security Council against the ruling Taleban movement on Sunday over its failure to hand over the Islamic militant Osama bin Laden.

The BBC's Kate Clark: "Demonstrators denounced the United States but not the UN"

Taleban spokesman Noorulla Zadran called the sanctions cruel and inhumane. He said that orphans and widows would be the ones to suffer.

He told the BBC that Afghanistan had tabled at least four proposals to resolve the issue, and all had been refused.

The sanctions ban the state airline Ariana from flying outside the country, and freeze the Taleban government's overseas bank accounts. Aid programmes will not be affected.

'Good Muslim'

Within hours of the order taking effect, young men swarmed onto the streets of Kabul, chanting "death to America", "long live Islam" and "Osama is a great Muslim".

Order was maintained despite attacks on UN buildings

The United States is considered to be the main force behind the sanctions.

The protesters stormed two UN compounds, but were beaten back by Taleban soldiers.

Mr bin Laden, who is living in hiding in Afghanistan, is accused by Washington of masterminding last year's US embassy bombings in Kenya and Tanzania.

Washington wants the Saudi exile extradited on terrorism charges and led efforts to impose punitive sanctions against the Taleban.

Open roads

In the statement broadcast on the Voice of the Islamic Republic of Iran, the Tehran embassy of the Islamic State of Afghanistan urged the UN to ensure the Taleban opened roads through which food and medicine could be delivered to the people of Afghanistan.

Food prices have already begun to climb in Kabul and the Afghan currency has fallen in the wake of the sanctions.

The BBC's Khalid Javed: "The UN offices bore the brunt of the demonstrators' wrath"

Residents in Kabul said they feared sanctions would hit ordinary Afghans.

Taleban Foreign Minister Wakil Ahmad Muttawakil made it clear that Kabul would not bend to pressure and urged other Muslim countries to ignore the sanctions.

"Our stance is the same, we will not hand over Osama to the US or expel him from Afghanistan against his will," Mr Muttawakil said.

The Taleban say their traditions do not allow them to hand over a "guest" to his enemies.