Two Iranian warships have entered Sudan's territorial waters and were heading to dock for "routine" fuelling, a spokesman of Sudanese army said on Wednesday.

"Two Iranian ships have entered our territorial waters, one of them is a destroyer and the other is a supplies vessel," Colonel Sawarmi Khaled Saad told AFP.

He said the vessels are stopping in Sudan for a "routine and regular visit" to get "supplies, food and water".

In October, two Iranian navy vessels called at Port Sudan, followed by two more in December, in what Khartoum described as a "normal" port stop.

Israel considers the area of the Red Sea and east Sudan as a passage for arms smuggled to Islamist Hamas movement in the Gaza Strip.

Khartoum's links with Iran came under scrutiny after Sudan accused Israel of being behind an October 23 strike against the Yarmouk military factory in the capital, which led to speculation that Iranian weapons were stored or manufactured there.

Last month, Saudi authorities denied permission for a plane carrying Sudanese President Omar al-Bashir to cross its airspace for the swearing-in of Iran's new president.

Riyadh said Bashir's flight plan lacked prior approval.