Cotabato, Philippines (Agencies): Weeks of clashes between rival Muslim rebel groups in the southern Philippines have left 13 people dead and forced thousands of others to flee their homes, the military said.

More than 1,000 rebels armed with rifles, rocket-propelled grenades and mortars have been involved in the fighting, as the two sides seek control of valuable farmland on Mindanao island, local army commanders said.

"One group will attack the other, and then break off. The other group will then stage an attack in retaliation. It is a series of skirmishes," regional military spokesman Major
Marlowe Patria told the press.

He said 13 fighters from both sides had been killed and nine others wounded since the clashes began on January 9.

Another 800 families had been evacuated to escape the fighting, which was occurring in rice fields and rural villages about 60 kilometres (40 miles) from Cotabato City, a main trading centre of the south, according to Patria.

The feud is between a Commander of the Moro National Liberation Front (MNLF), the country's original Muslim separatist group, and a Commander from the breakaway Moro Islamic Liberation Front (MILF), he said.

MILF spokesman Mohager Iqbal said the two commanders were fighting over 1,000 hectares (2,470 acres) of riceland, while emphasising the dispute was a local one and not between the main groups.

The local government as well as the leadership of the MNLF and MILF has been trying to broker a ceasefire this week, but fighting continued on Wednesday and there were fears the conflict could escalate.