The White House’s closest Persian Gulf allies have been handing out sophisticated American weapons to al Qaeda and dangerous groups in Yemen in violation of US an export rules, an investigation by CNN has revealed.

According to a investigation by the broadcaster, Saudi Arabia and the United Arab Emirates, the two countries now leading a disastrous four-year war against Iranian-backed Houthi rebels in Yemen, have been doling out American weapons to local allies that include groups tied to al Qaeda and other armed extremists hostile to the US.

Occasionally, the weapons have also fallen into the hands of vocally anti-Western Houthi rebels, a consequence of battlefield chaos in Yemen.

Separately, The Independent has seen an investigation by advocacy group Amnesty International, set to be released on Wednesday, alleging that the UAE has distributed advanced weaponry it has received from dozens of countries to Yemeni militias with little accountability or oversight.

The Amnesty report documents the distribution of US armoured vehicles equipped with heavy machine guns into the hands of several militias allied with the UAE.

Yemen is subject to interlocking, obscure, and ever-changing tribal loyalties that overlap with the armed groups tied up in the war. Some parts of the country remain under the sway of the local affiliate of al Qaeda or like-minded groups.

CNN reports that the Saudi-led coalition uses American weapons “as a form of currency to buy the loyalties of militias or tribes, bolster chosen armed actors, and influence the complex political landscape”.

Such distribution violates the terms of US weapons export rules. The Pentagon says it is investigating the allegations, which add to pressure on Saudi Arabia after spies and assassins close to the royal court ignited a global uproar abducting, murdering, and dismembering Washington Post journalist Jamal Khashoggi last year.

Weapons cited in the CNN report include US-made TOW antitank missiles, MRAPs (Mine-Resistant Ambush Protected vehicles), Oshkosh armoured vehicles, assault rifles sold on the black market, handguns, and pistols, as well as ammunition.

Mukalla: Ex-Al Qaeda stronghold in Yemen Show all 22 1 /22 Mukalla: Ex-Al Qaeda stronghold in Yemen Mukalla: Ex-Al Qaeda stronghold in Yemen Young recruits from Mukalla's new police academy attend their graduation ceremony after a UAE-led six-week training course Bel Trew/The Independent Mukalla: Ex-Al Qaeda stronghold in Yemen Yemeni soldier on the look out for militants or smugglers from his look out post over Mukalla Bel Trew/The Independent Mukalla: Ex-Al Qaeda stronghold in Yemen Afrah Jamaakhan, Yemen's first female radio director, says they have rebuilt Mukalla's radio station after al-Qaeda torched the old building Bel Trew/The Independent Mukalla: Ex-Al Qaeda stronghold in Yemen Soldiers guard the streets of Mukalla, a former al-Qaeda stronghold in south Yemen Bel Trew/The Independent Mukalla: Ex-Al Qaeda stronghold in Yemen An Emirati pilot in a Chinnok overlooking Eritrea on a flight back from Yemeni military bases Bel Trew/The Independent Mukalla: Ex-Al Qaeda stronghold in Yemen Emirati-supported look out points dot the mountains surrounding Mukalla Bel Trew/The Independent Mukalla: Ex-Al Qaeda stronghold in Yemen UAE armoured truck at Mukalla's strategic port Bel Trew/The Independent Mukalla: Ex-Al Qaeda stronghold in Yemen The city of Mukalla, which for a year was al-Qaeda's stronghold in Yemen Bel Trew/The Independent Mukalla: Ex-Al Qaeda stronghold in Yemen Soldiers guard the streets of Mukalla Bel Trew/The Independent Mukalla: Ex-Al Qaeda stronghold in Yemen Dr Fatma whose husband was kidnapped by al-Qaeda Bel Trew/The Independent Mukalla: Ex-Al Qaeda stronghold in Yemen A wooden boat docks at Mukalla port Bel Trew/The Independent Mukalla: Ex-Al Qaeda stronghold in Yemen Maj-Generaal Faraj Salmin al-Bahsani, governor of Hadramawt, at his offices in Mukalla Bel Trew/The Independent Mukalla: Ex-Al Qaeda stronghold in Yemen Mukalla's new radio station, the old building was burnt down by al-Qaeda Bel Trew/The Independent Mukalla: Ex-Al Qaeda stronghold in Yemen Mukalla port Bel Trew/The Independent Mukalla: Ex-Al Qaeda stronghold in Yemen New Emirati-trained police graduates gather for their graduation ceremony Bel Trew/The Independent Mukalla: Ex-Al Qaeda stronghold in Yemen Mukalla from an observation post over looking the city Bel Trew/The Independent Mukalla: Ex-Al Qaeda stronghold in Yemen The UAE said it has delivered 60 police bikes to Hadramawt to support the police forces Bel Trew/The Independent Mukalla: Ex-Al Qaeda stronghold in Yemen A panorama of Mukalla, south Yemen Bel Trew/The Independent Mukalla: Ex-Al Qaeda stronghold in Yemen A commercial vessel docks at Mukalla port which officials hope will become a major business hub Bel Trew/The Independent Mukalla: Ex-Al Qaeda stronghold in Yemen The UAE said it has donated over 150 police trucks to Hadramawt's new police force Bel Trew/The Independent Mukalla: Ex-Al Qaeda stronghold in Yemen UAE security forces drive through town in armoured cars fearing attacks from militant sleeper cells within Mukalla Bel Trew/The Independent Mukalla: Ex-Al Qaeda stronghold in Yemen Afrah Jamaakhan, Yemen's first female radio director, at Mukalla's new radio station Bel Trew/The Independent

In 2017, a pro-Houthi television channel showed images of rebels driving an MRAP through Sanaa while the crowd chanted “Death to America.” CNN cited a Houthi official as saying Iran has already obtained an MRAP and could reverse engineer the vehicle, which was designed in part to thwart sophisticated roadside bomb attacks launched by Iranian-backed militias in Iraq.

“There isn't a single American weapon that they don't try to find out its details, what it's made of, how it works," the source told CNN.