Afghan affairs analyst Ahmed Rashid: "Iran's target may be the city of Herat"

A statement read by an announcer said: "Tehran has tried...to make the (United Nations) Security Council aware of a situation which can threaten international peace and security.

"After this process, Iran will have the right under Chapter 7, Article 51 of the UN Charter to take all necessary action in the context of legitimate defence."

The announcement came shortly after American defence officials told the Washington Post newspaper they believed Iran was about to launch a raid into Afghanistan.

Troops mass

Iran earlier this week sent 70,000 troops to the border - along with tanks, heavy artillery and attack aircraft - for military exercises.

Soldiers from the elite Revolutionary Guards have been testing their weapons - including Sam-6 medium-range missiles within view of the Afghan border.

The Afghan Islamic Press news agency says the Taleban has started arming civilians in the western province of Nimroz in case of an Iranian attack.

BBC correspondent Richard Galpin, who is monitoring the situation from Islamabad, says Iranian troops have staged mock assaults, simulating incursions deep into enemy territory.

BBC's Richard Galpin reports

The Iranian authorities announced this week the troops would remain in the area even after the manouevres have finished.

Major-General Safavi...insists Iran is not looking for confrontation

The commander of the Revolutionary Guards, Major-General Yahya Rahim Safavi, said his men would simulate attacks deep into enemy territory. But he denied Iran was seeking confrontation.

Tension brought to boiling point

The tension between Kabul and Tehran has been simmering for some time.

But it has been brought to boiling point by fears for the safety of 10 Iranian diplomats and a journalist who went missing when the Taleban captured the opposition stronghold of Mazar-i-Sharif in northern Afghanistan last month.

Iran, which provides both military and financial help to the Afghan opposition, has been alarmed by the recent military successes of the Taleban, whose extreme brand of Sunni Islam is vary different from Iran's own radical Shia ideology.

While Iran believes its diplomats have been taken prisoner the human rights organisation Amnesty International said this week they had been killed.

Amnesty quoted eyewitnesses as saying the bodies had been left outside the Iranian consulate in Mazar-i-Sharif for two days before being buried in a mass grave.