Iranian warships clashed with pirates in the Gulf of Aden thwarting an attempt to seize three Iranian commercial vessels, the official IRNA news agency reported on Monday.

"The Iranian navy contacted the unknown boats which approached three Iranian ships," IRNA said quoting a navy statement.

After "they ignored the warnings, the warships took action, fired shots and drove the pirates away," it said, without specifying when the incident took place.

In May, Iran sent two warships to patrol the Gulf of Aden and protect its oil tankers and other commercial shipping from pirates operating off the Somali coast.

In January, Iran's state broadcaster reported that Somali pirates had released a Hong-Kong registered cargo ship chartered by Iran which had been hijacked in the Gulf of Aden in November.

Last October, the authorities in Tehran paid a ransom to secure the release of an Iranian merchant vessel hijacked off the Somali coast two months earlier.

Pirates have carried out more than 100 attacks in the key shipping lane that links the Indian Ocean with the Mediterranean through the Suez Canal since the start of this year.

A raft of navies from around the world have sent naval vessels to the area to combat the threat.