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NIAMEY, July 12 (Reuters) - Tuareg-led rebels in Niger have fired mortars in an attack on the main town in the uranium-producing north, but authorities said on Saturday there had been no serious damage or casualties.

The Niger Justice Movement said its fighters launched the raid on the garrison town of Agadez late on Thursday to counter government claims the rebels had been weakened by the death of their deputy commander in battle last month.

"This raid is the prelude to an offensive ... we are going to launch on Niger's army and the authorities in Niamey," the rebel group said on Saturday on its website http://m-n-j.blogspot.com/, urging civilians to move away from military posts and governmental buildings.

Agadez governor Abba Malam Boukar told Radio France Internationale (RFI) that the rebels failed in their attack.

"There was some rocket and heavy weapons fire ... but they failed in this raid on Agadez," Boukar said.

Several shells landed near his residence and the hospital, but caused no damage, he added.

Nigerian President Mamadou Tandja's government dismisses the rebels as bandits and smugglers of arms and drugs and has ruled out talks with them until they first lay down their weapons.

At least 200 rebels and 70 government soldiers have been killed since the rebellion was launched over a year ago.

Riding the tide of rising uranium prices, Niger is attracting investors and hopes to become the world's second largest producer by 2011, largely thanks to new mines being opened by France's Areva and the China Nuclear International Uranium Corporation.

The rebels say northerners are not benefiting from their country's resources. In the past rebels have kidnapped miners before releasing them unharmed. (For full Reuters Africa coverage and to have your say on the top issues, visit: http://africa.reuters.com/) (Writing by David Lewis and Ingrid Melander, Editing by Matthew Jones)

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