(CBS) A Moroccan government official says three Saudi suspected members of al Qaeda have been arrested on charges of planning "terrorist attacks" on U.S. and British ships in the Straits of Gibraltar.

"Morocco's security services have dismantled a network of al Qaeda who planned terrorist attacks on U.S. and British warships crossing the Straits of Gibraltar... It was a successful operation," said the official, who declined to be named, at a private briefing.

The official said the three men, holding Saudi passports, were arrested in Morocco last month. He declined to name them, saying only they were aged between 25 and 35.

He said the men planned to sail small dinghies carrying explosives into the Straits of Gibraltar.

Moroccan government officials say the men were arrested last month and claimed to belong to Osama bin Laden's al Qaeda network.

The official said they were planning an attack similar to the raid on the U.S. warship Cole while it was refuelling off Yemen in 2000. Washington blamed that suicide attack, which killed 19 sailors, on al Qaeda.

Earlier on Monday, U.S. authorities said they had captured a suspected American al Qaeda operative carrying out reconnaissance for an attack on the United States with a radioactive "dirty bomb."

The three Saudi nationals were being held in custody in Casablanca prior to interrogation by the prosecutor, the Moroccan official said.

In Washington, a U.S. intelligence official who spoke on condition of anonymity said: "We have been very well aware of it." Asked if by "it" he meant the report or the arrest, he said "the arrest." The official declined further comment.

A spokesman for Britain's Foreign Office said the government was awaiting further information.

"We welcome the arrests if they involve individuals who may have been planning terrorist attacks against UK assets," he said.

He said they were funded and supported by Saudi-born Osama bin Laden, head of the al Qaeda network and the key suspect in the September 11 suicide hijacking attacks on the United States.

A veteran Western diplomat said the planned "terrorist" operation was aimed at hitting NATO warships, mainly U.S. and British ships from the Spanish enclaves of Ceuta and Melilla.

The arrests were made with the help of intelligence services of
"several friendly countries," according to the official, who cited close cooperation between U.S., British, French, Spanish and other Western and Arab intelligence services.

It is the first time since the Sept. 11 attacks that such a group has been discovered in Morocco.

In a suicide attack linked to al Qaeda in Tunisia last April, 21 people, including 14 German tourists, were killed near a synagogue.