Ndjamena/Nairobi - Chadian President Idriss Deby announced on Thursday that his army had secured control of the capital Ndjamena where heavy fighting with rebels was reported earlier - but rebels insisted their advance was continuing.

"The rebel columns have been entirely destroyed and there is now only some light weapon fire near the National Assembly, but the situation is now completely under control," Deby told French radio Radio France Internationale (RFI).

Heavy artillery fire was reported in and around Ndjamena as rebels battle fight government troops for control of the capital and to oust president Deby's 15-year rule ahead of planned May 3 presidential elections.

In contrast, a United Front for Change (FUC) rebel spokesperson speaking to the French radio from Paris said that their forces were currently marching towards the presidential palace.

Ndjamena has accused neighbouring Sudan of assisting the rebels in their latest multipronged attacks in the capital and the eastern garrison town of Adre, near the border with Sudan.

Foreign missions have advised their nationals to stay indoors while the United Nations has started moving non-essential staff to neighbouring Yaounde, according to a UN official in Ndjamena.

Deby is reportedly still in the city, relying mostly on 1 200 French troops in the former French colony. France reinforced the force with 150 men and six military aircraft from French bases in Gabon Wednesday.

Owing to its central location in Africa, Chad plays an important role for the stability of the continent, a French defence ministry spokesperson said.

France was providing the "rightfully elected government" of President Idriss Deby with data from reconnaissance flights over the area where fighting was taking place.

The 54-year Deby has been increasingly isolated since his former top advisers and twin nephews, Tom and Timane Erdimi joined the exiled rebellion last year, sparking mass defections from his army. - Sapa-dpa