The Iranian armed forces are holding a large-scale exercise in the Gulf.

Up tofifty-thousand troops are taking part in the five-day operation, along with naval ships and aircraft.

Such exercises have, in the past, been viewed with suspicion by Arab Gulf states.

But the BBC Gulf corresponent says the Iranians have recently been promoting the idea of Islamic co-operation in the region,and announced this week that the war games would be watched by observers from Oman with whom Iran signed a defence treaty in November.

Iran has repeatedly denounced the presence of Western navies in the Gulf, and our correspondent says Tehran now hopes to re-establish itself as the leading military force in the region - a role it lost with the fall of the Shah twenty years ago