GRAND BEREBY, Ivory Coast -- A cease-fire between two Ivory Coast rebel groups and government forces began Saturday afternoon, even before the insurgents formally signed a truce, a senior French military officer said, AFP reported.

The officer, speaking on condition of anonymity, said the truce began at noon (1200 GMT) on the south-western front. A formal cease-fire agreement was due to be signed later.

"The rebels have pledged to respect the cease-fire and stop any movement southwards," he said.

He said the government forces in the area had not yet received orders to "stop their offensive," but added: "The cease-fire line will come into being one day," and that both sides had indicated that the truce would be respected.

The Ivorian Popular Movement of the Far West (MPIGO) and the allied Movement for Justice and Peace (MJP), two Western-based groups who have continued fighting the government, are to sign a cease-fire in Togo later Saturday, diplomatic and military sources said.

The truce will be signed under the auspices of the 15-nation Economic Community of West African States (ECOWAS), which has mandated Togolese President Gnassingbe Eyadema to mediate in the four-month Ivorian war.

The two movements had steadfastly refused to join an October 17 truce between the main rebel group the Patriotic Movement of Ivory Coast (MPCI) and the government.

The truce comes ahead of key French-brokered peace talks in Paris due to start on Wednesday.

Some 2,500 French peacekeepers are enforcing a shaky truce between the MPCI and the government which recently pledged to France that they would not break the often-violated cease-fire.