OUAGADOUGOU (Reuters) - Mali's interim leader has made a formal request to west African regional body ECOWAS for military assistance to help free the country's north, which has been occupied since April by Islamists, France's special representative for the Sahel said on Tuesday.

Jean Felix-Paganon said he was informed of the decision during a meeting with Ivorian President Alassane Ouattara, who chairs the 15-nation Economic Community of West African States (ECOWAS).

"President Ouattara informed us that President (Dioncounda) Traore had formally sent a request to ECOWAS for military assistance to stabilise the country and especially to the reconquer the north," Felix-Paganon told journalists in neighboring Burkina Faso.

"It is an important development which we examined the possible outcomes with President (Blaise) Compaore," Felix-Paganon said after meeting with Burkina Faso's president in Ouagadougou late on Tuesday.

The French diplomat did not give details of the request nor when it was made. Ecowas has said it was ready to send about 3,000 troops to Mali to help take back the north.

Leaders of the west African bloc have been waiting for a formal request from Malian authorities, which will enable the bloc and the African Union seek a United Nations Security Council mandate to send troops to the country.

In June, the Security Council asked the African Union and West African group ECOWAS to explain more precisely what kind of resolution they wanted.

Felix-Paganon said the African Union will be informed at some point and it will be left to African leaders to decide at what time they intend to refer the request to the Security Council.

Once regarded as a good example of African democracy, Mali was plunged into chaos in March when soldiers toppled the president, leaving a power vacuum that enabled Tuareg rebels from the north to seize nearly two thirds of the country.

The Tuareg rebellion has since been hijacked by Islamist militants who have began imposing sharia law in the three northern regions of Gao, Kidal and Timbuktu now under their control.

(Reporting by Mathieu Bonkoungou; Writing by Bate Felix; Editing by Jackie Frank)