(adds hostage release paragraphs 8-11)

By Abdoulaye Massalatchi

NIAMEY, Aug 4 (Reuters) - France's Secretary of State for Cooperation hailed progress on Saturday in ending a row over accusations that nuclear group Areva backed rebels in Niger, and he offered French aid in demining the restive northern region.

After a meeting with Niger's President Amadou Tandja, Jean-Marie Bockel said the French government would organise a summit of foreign ministers from across Africa's arid Sahel belt to discuss security in the region.

Niger, France's main supplier of military grade uranium, has accused Areva of financing Tuareg-led northern rebels and last month barred its local representative from the country. The French government and Areva have denied the allegations.

"There have been very significant advances in the willingness to overcome certain misunderstandings," Bockel said after the meeting, without giving further details. "It is clear that Areva never supported and does not support the rebellion.

"I have offered French help in demining the north because we have a certain degree of expertise in this area," he said.

At least seven soldiers have been killed by landmines over the last month in the desert region around the ancient caravan route of Agadez.

Tandja's government has already appealed to neighbouring countries for support in ending the six-month uprising by the Niger Movement for Justice (MNJ), which has killed more than 40 soldiers.

Libyan leader Muammar Gaddafi has met with the MNJ's leaders to call for them to lay down their arms. His mediation led to the release on Saturday of some of the dozens of soldiers held hostage by the Tuareg group, a national parliamentarian from the northern region said.

"Some of the prisoners have been released and we think more will follow," said Brigi Raffini, spokesman for a delegation of officials and tribal chiefs from the Agadez region calling on the rebels to negotiate.

A military source said at least six soldiers had been freed.

"This has happened thanks to the efforts of ... Gaddafi," said Raffini. "Today, we can now consider ourselves at the start of a peace process."

Areva, which operates two uranium mines in northwest Niger with production of over 2,000 tonnes a year, signed its annual pricing convention with the government, hiking the price it paid for uranium to 40,000 CFA francs ($83.59) per kg this year from 27,300 last year. The agreement is retroactive to Jan. 1.

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