By Tiemoko Diallo

BAMAKO, Aug 28 (Reuters) - Suspected Tuareg gunmen seized a military supply convoy in northern Mali, their second attack in two days and the latest sign of a concerted campaign with Tuareg rebels in neighbouring Niger, military sources said on Tuesday.

The ambush by a group of armed men crossing the desert in Toyota pick-ups took place on Monday some 50 km (31 miles) from the town of Tinsawatene, in Mali's desolate northern reaches, the sources said.

Some soldiers were injured and several attackers killed during hours of fighting before the rebels escaped with a supply truck, two Toyota vehicles and some prisoners.

"We do not know the death toll yet but many Toyotas were burned and many of the attackers were killed," said a senior Defence Ministry source.

On Sunday, suspected Tuareg gunmen abducted about 25 Malian soldiers in a remote Saharan town and took them off toward Niger, where the nomadic tribesmen have been waging a campaign for seven months, which has killed more than 45 soldiers. The mountainous area where Sunday's abduction took place is regarded as a stronghold of Tuareg leader Ibrahima Bahanga, whom Malian authorities accuse of killing a gendarme in an attack in May backed by rebels from the Niger Movement for Justice (MNJ).

"We are obliged to work closely with Niger because we believe there are links between the two groups," said the senior defence source.

"When they launch attacks in Niger they seek refuge in Mali, and when they attack in Mali they hide in Niger."

"There are contacts under way between military authorities in Mali and Niger to secure the area," the source added.

Last week, Mali and Niger's security ministers met in the eastern Malian town of Gao and signed a deal allowing each others' security forces to pursue suspected bandits across their common border.

Bahanga, one of the leaders of a Tuareg revolt in the 1990s which won greater autonomy for the light-skinned tribesmen in Mali and Niger, has been disowned by a broader Malian rebel alliance, which signed a deal with President Amadou Toumani Toure in July 2006.

Toure, during a weekend visit to Tripoli, said he had agreed with Libyan leader Muammar Gaddafi to hold a regional summit on security in the Sahel.

Niger President Mamadou Tandja has also appealed for regional support in quelling the uprising, which his government has accused French nuclear power company Areva <CEPFi.PA> and "rich foreign powers" of supporting.

The company has strongly denied this.

Niger's government said on Tuesday it had demined and reopened the road between the northern uranium mining hub of Arlit and the oasis town of Iferouane, which lies more than 1,000 km (600 miles) from the capital Niamey and has been isolated for more than two months.

A military convoy was able to deliver 60 tonnes of emergency food aid to the settlement, which lies in the heart of the rebel zone and was the scene of its first attack in February. (Additional reporting by Abdoulaye Massalatchi in Niamey)

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