It's not the first time that U.N. vehicles have been used to carry jihadi explosive weapons, but the man-bites-dog element of this story is that the intended target was not Israelis, but the U.N. From AP:
MOGADISHU, Somalia – Islamist suicide bombers in explosives-laden cars with U.N. logos drove onto the main base of African Union peacekeepers Thursday and triggered two massive blasts that a witness reported killed at least 11 people, blew out windows and shrouded the sky in black smoke.
"I have counted the bodies of 11 people, Somalis and peacekeepers," the witness said, requesting anonymity for fear of reprisals.
The AU said peacekeepers were wounded in the attack at Mogadishu's airport, but did not elaborate. The African Medical and Research Foundation, which operates a flying doctors service, said the U.N. has asked for help evacuating 15 "critically injured" people.
An Islamist insurgent group claimed responsibility for the attack and said the targets were senior peacekeeping officials and Somali government officials who were meeting there. The attack came two days after al-Shabab vowed revenge for a U.S. commando raid that killed al-Qaida operative Saleh Ali Saleh Nabhan in Somalia.
[...]
"The soldiers at the gate assumed they were U.N. cars and opened the gate for them," the security official said, asking that his name not be used because he is not authorized to speak to the media. "When the cars entered one of them sped toward a petrol depot and exploded. The other one exploded in a nearby area."
U.N. spokeswoman Benedict Walter says the organization has not confirmed the vehicles used were U.N. cars.
Either this attack was planned much further back than two days ago (in which case the claim that this was retaliation for the U.S. commando raid is a complete fabrication),
- or the jihadis were extremely resourceful in purchasing U.N.-like vehicles (in Somalia) and painting them in U.N. logos, and contructing and installing an explosive device, within two days,
- or the jihadis have access to U.N. vehicles.