Kabul, Afghanistan ? A powerful and sophisticated type of roadside bomb prevalent in Iraq but not seen before in Afghanistan was discovered near a university in Kabul last week, prompting a rare countrywide warning to NATO and Afghan troops.

The bomb, known as an EFP, or explosively formed projectile, was notable for its level of sophistication and similarity to those seen in Iraq, said Maj. John Thomas, a spokesman for NATO’s International Security Assistance Force.

NATO officials say they don’t know where the bomb came from.

“The kind that we’re talking about is machined. It has to be fabricated to pretty certain specifications … by somebody who knows what he’s doing,” Thomas said. “The next question is how similar is it to those made in Iraq, and the answer is considerably similar.”

Thomas said there was no evidence to suspect a certain manufacturer, nation or even region as the source. He said Iran or al-Qaida elements in Iraq or Pakistan were possibilities.

NATO sent out a warning to international and Afghan troops to watch out for EFPs. The warning, shown to The Associated Press by a security official who asked not to be named because it is an internal document, said the sophisticated bomb was found May 26 near a Kabul university. It said lesser-quality EFPs were found in Herat, near the Iran border, in April.

Thomas confirmed NATO issued the warning, saying the rare Afghanistan-wide message showed it was concerned.

“The guys who are working counter-IEDs (improvised explosive devices) are professionally alarmed in the sense they were hoping they wouldn’t see these” in Afghanistan, Thomas said.