ANALYSIS-Chad rebel moves test EU force

By Pascal Fletcher

DAKAR, June 18 (Reuters) - A hit-and-run offensive by rebels in Chad has tested the strength and neutrality of a European Union military force deployed to protect refugees in the east of the African state that borders Sudan's Darfur region.

The mobile rebel columns of armed pickups have raced through towns and struck at army posts in the eastern borderlands. But they have not attempted to repeat the headlong charge westwards to the capital N'Djamena that they made in February.

Analysts see a possible shift in tactics by the insurgents, who have fought for more than two years to try to topple President Idriss Deby. Himself a former rebel, Deby says they are "mercenaries" fighting on behalf of neighbouring Sudan.

The anti-Deby rebel National Alliance briefly occupied at least four small towns over the last week in raids which again stoked tensions between Chad and Sudan. Their long common frontier runs along Sudan's conflict-torn Darfur region and they both accuse each other of supporting armed groups.

But unlike their February assault on N'Djamena, which failed to overthrow Deby, the rebel columns this time harried the Chadian army in the east in an apparent war of attrition.

"The rebels are staging a show of strength and seeking to underline President Deby's weakness and inability to control the whole Chadian territory," Bjoern Seibert, an analyst at Boston's Fletcher School of Law and Diplomacy, said.

The rebels accompanied their offensive with announcements of combat successes by spokesmen based in France and Sudan who called foreign media organisations with satellite phones.

"It's a war of Thurayas (satphones), not Kalashnikovs," said Chadian Information Minister Mahamat Hissene. He said the start of the rainy season also hampered the rebel advance.