Islamist militants in Somalia are receiving arms from Yemen and Iran, Western diplomats told Reuters.

The arms trade networks involved in the scheme would be in breach of a U.N. embargo on weapons exports to Somalia.

A monitoring team sent by the U.N. Security Council raised the concerns over the arms shipments as Yemen is requesting Iran stop backing insurgent groups on its soil.

Most of the weapons enter Somalia via the two northern autonomous regions of Puntland and Somaliland before being transported south to Al Shabaab rebels.

The monitors found the North Korean- and Iran-made weapons at a base of the U.N.-backed African Union (AU) peacekeeping force in Somalia, which raises the question of the possibility of arms smuggling networks operating within the AU force.

The weapons are said to include improvised bombs and Russian-designed PK machine guns.

"Why are Iranian and North Korean small arms finding their way into Somalia from Libya? Do they date from before the arms embargoes [against both North Korea and Iran]? How did they get there from Libya?" a council diplomat asked Reuters.

The U.S. is pushing for an end to the 21-month arms embargo, imposed in 1992.

"There are no Somali warlords that threaten peace and stability in Somalia," the alternate permanent representative for Somalia, Idd Beddel Mohamed, told Reuters. "They are normal citizens now, members of parliament. The embargo must be lifted."