(Adds security source quotes, details, background)

By Andrew Heavens

KHARTOUM, Feb 10 (Reuters) - Sudan has arrested two Muslim "fundamentalists" in connection with the killings of a U.S. aid official and his driver in the capital Khartoum, security sources said on Sunday.

The two men, aged 25 and 30, were members of a group that was also behind a plot to bomb Western embassies in Khartoum that was uncovered in August, the security source told Reuters.

It was the first official confirmation that a militant group may have been behind the double shooting. Some official sources in Sudan originally claimed that the killing was an "isolated incident".

The suspects opened fire when they were cornered on Saturday in a suburb of Omdurman, a city adjacent to the Sudanese capital, the SUNA state news agency reported. Security officers returned the fire.

Two policemen, a passing woman and the two suspects were wounded, none seriously, said the security source.

"They are from the same group who tried to do the explosions ... they are fundamentalists," the source added, referring to the reported August bomb plot.

A spokesman for the U.S. embassy in Khartoum declined to comment on the reports of the arrests.

John Granville, a 33-year-old officer with the U.S. Agency for International Development, was killed by gunmen while returning home from New Year celebrations in Khartoum on Jan. 1. His driver, Abdelrahman Abbas Rahama, 39, was also killed.

Days after the attack, a previously unknown group calling itself Ansar al-Tawhid (Companions of Monotheism) in Sudan, posted a message on a Web site used by militants claiming responsibility for the killings.

Granville was the first U.S. government official to be killed in Khartoum in more than three decades.

U.S. agents from Diplomatic Security and the Federal Bureau of Investigation flew in to help with investigations.

In August, Sudanese security services said they had broken up a plot to attack the French, British, U.S. and U.N. diplomatic missions in Khartoum. The group was discovered in a Khartoum house after explosives went off by accident, according to international sources.

At the time, authorities said they had seized weapons and arrested most of the plotters, although a number had managed to get away.

Foreign embassies in Khartoum tightened security after claims about the bomb plot emerged and ratcheted up precautions still further after the New Year's Day killings.

SUNA said security forces had tracked the two suspects down to the suburb of Al-Fitaihab in Omdurman after a tip-off.

Quoting the police press department, SUNA reported that the two suspects had opening fire on security forces who had come to arrest them, injuring some members and one civilian.

"...the suspects were arrested, the injured were given medical treatment and put under arrest". (Additional reporting by Opheera McDoom; editing by Sami Aboudi)

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