Drills reportedly simulated a pirate seizure of two vessels. The Iranian spokesman for the drills, Admiral Mustafa Tajeddini, said "naval and aerial units of the three countries liberated two merchant ships hijacked by pirates in international waters".

Such attacks in the region are generally undertaken by Somali pirates, who in early November reportedly attempted to seize Iranian oil tankers in the Gulf of Aden for the second time in two weeks.

A vessel was headed towards the Bab al-Mandeb strait at the entrance to the Red Sea when six pirates aboard several vessels attempted to board it on November 1, drawing warning shots from the Iranian navy, ISNA news agency said at the time.

This was preceded by a similar attempt on October 16, when an Iranian warship repelled an attack by pirates against two oil tankers that it was escorting in the Gulf of Aden, the country's naval chief said.

The Bab al-Mandeb strait is a strategic transit path linking the Red Sea and the Gulf of Aden on a route commonly used by vessels heading to Europe via the Suez Canal.

IRNA reported that the joint drill would include "aerial and surface units of the Iranian navy, the Revolutionary Guards, and Chinese and Russian maritime forces".

Spokesman Tajeddini stated that the exercises are taking place "within the framework of serious security and military cooperation (between the three countries) to counter existing threats".

The manoeuvres follow Iranian President Ebrahim Raisi's official visit to Moscow on Wednesday, where he said Tehran has "no limits for expanding ties with Russia".

The drills also come during talks in Vienna aimed at salvaging a 2015 nuclear deal between Iran and world powers, including Russia and China.

The exercises will continue for three days and will take place over an area of 17,000 square kilometres (almost 6,600 square miles) in the northern Indian Ocean.

Tajeddini said that they aim to "enhance capabilities and combat readiness, strengthen military ties between the Iranian, Russian and Chinese navies, ensure common security and counter maritime terrorism".