The Iranian military has begun a week-long simulation of air defence exercises aimed at practising responses to possible attacks on the country's nuclear sites.

The drills were announced on Saturday by Brigadier General Ahmad Mighani, the head of Iran's army air defence, who said the war games were due to threats against the country's controversial nuclear facilities.

"It is our duty to defend out nation's vital facilities and thus these manoeuvres covers Bushehr, Fars, Isfahan, Tehran and western provinces," he said.

Tensions are high between Tehran and the six world powers trying to negotiate a deal on Iran's nuclear programme.

Western powers believe that Iran's enrichment work is masking an atomic weapons programme but Tehran insists it is purely for generating electricity.

Meanwhile, Washington and Israel have never ruled out a military strike against Iran's nuclear sites, but the Islamic republic has warned it will hit back at Israel and US interests in the region if it is attacked.