Two Yemeni fishermen were killed and one was injured while the fate of a fourth one is still unknown after their boat came under an aggressive assault by one of the international naval ships patrolling the Red Sea near Sudan on Tuesday.

A source at the Coast Guard said Abdu Marwani and Muhammad Naj'e were killed immediately after their boat was totally destroyed by a missile which some suspect was an air strike.

Sources at Yemen's navy said it probably came from sea.

While the third fisherman made it to Sudanese coast and is now in critical condition.

The fishermen came from the Midy area, Hajjah before their boat was hit near Sudan's waters.

A coordinated investigation by Yemen and Sudan is underway to explore reasons for the attack.

Meanwhile, director of the Midy district Abdul Majeed Al-Himyari dismissed reports a Yemeni boat was attacked in Yemen's territorial waters, saying the incident took place while the boat was in Sudan's territorial waters.

He told the media the survivor is being investigated by Sudan.

Tuesday's attack comes in a series of attacks against Yemeni fishing boats by international forces patrolling the Red Sea and the Indian Ocean.

Early this year, two Yemeni sailors were killed as their boats came under separate attacks by international troops in the Indian Ocean. Few others were hurt, with troops saying they suspected the boats were for pirates and then hit them.

And this month, the Interior Ministry said a Yemeni boat was provoked, with NATO's mission in the region intimidating its crew.

The area where the boat was hit on Tuesday is witnessing large fuel smuggling, with eyewitnesses affirming boats smuggle diesel to African Horn States daily.