``The Islamic Revolution Guards Corps (IRGC) started an unprecedented military exercise with participation of 70,000 elite forces in north-eastern Iran on Tuesday and the Ashura 3 war games are being launched at 600 square kms along the eastern border,'' official Iranian news agency IRNA SAID.

The Revolutionary Guards Commander Major General Yahya Rahim Safavi was quoted by the Iranian state television as telling the troops that Tehran would not tolerate ``open or secret interferences of foreign powers in its neighbouring countries nor threats to its security and peace.''

The troops would remain near the border even after the end of three-day massive military exercises there, he said.

Iran's foreign ministry spokesman Mahmoud Mohammadi said his country would do what itdeems necessary to secure safety and freedom of the Iranian diplomats and citizens allegedly held hostages in Afghanistan.

Meanwhile, Taliban today asked for UN mediation to ease tensions with Iran. ``The Islamic Emirate of Afghanistan is ready for any kind of mediation by the UN or by the Organisation of Islamic Conference,'' Taliban envoy to the UN said in a statement.

Meanwhile, intense fighting continued in Afghanistan with the Taliban claiming major gains in Northern parts including the capture of the key opposition base of Sheberghan.

If confirmed, the fall of Sheberghan would put the opposition capital of Mazar-i-sharif under serious threat, experts said.

Iran has evacuated staff at its mission in Mazar-i-sharif after the Taliban offensive, Iranian state radio reported in Tehran.