He said 200,000 troops, backed up by tanks and aircraft, had been involved in "a fruitful and positive operation".

Simon Bowden: "Up to 200,000 troops could be involved"

It was one of the biggest exercises ever held in the country, although some sources put the figures much lower.

During the manoeuvres, military units launched nocturnal assaults on mock enemy targets across more than 50,000 square kilometres in the Zabol region in the south-east of the country.

The Iranian news agency said the operation was conducted under the light of flares and with the support of artillery, mortar and missile units.

The diplomats' bodies were returned to Iran for burial

The exercises were announced in September as tension rose sharply following the killing of nine Iranian diplomats by Afghan Taleban troops as they seized the northern Afghan city of Mazar-i-Sharif from Iranian-supported opposition forces in August.

Iran sent thousands of troops to the border and started low level manoeuvres - it said the exercises were meant to deter smuggling and border aggression.

The final key phase of the operation was postponed until early on Monday while Iran awaited the outcome of United Nations mediation over differences with the Taleban.

The BBC Kabul Correspondent, William Reeve, says the UN special envoy, Lakhdar Brahimi succeeded in averting open war between the two countries.

The Taleban also stepped up their border presence

The Taleban have freed most of the Iranian prisoners they held in Afghanistan and agreed to meet the Iranian authorities face-to-face.

Iran still insists that the killers of its citizens be punished and that the Taleban abide by UN resolutions calling for broader government in Afghanistan.