Senegal's government is investigating who was behind a brutal attack in the restive southern Casamance region, in which more than a dozen farmers have had their left ears cut off while they were harvesting cashew nuts in the rebel-hit region. Ricci Shryock reports from Senegal's capital, Dakar.

Senegalese army spokesman Daouda Diop says rebels from the Movement for the Democratic Forces of Casamance might be behind Wednesday's attack on local farmers, but he is not ruling out other parties.

Three injured persons wait for assistance at an emergency room of Ziguinchor hospital, 07 May 2008

He says, in the attack, armed men are accused of having cut off each victim's left ear.

The rebels have been fighting a low-level insurgency in the region for decades. They have recently splintered into several groups.

A journalist in Ziguinchor, Alpha Jallow, spoke to one of the victims shortly after the attack.

"He said that when they were just at the farm, they were rounded up by about 10 of these gunmen, and they said that 'We are going to give you a lesson that you will never forget, and then when you go the government and the Casamance people will know that the land, we still control the land and you have no right to come here,'" said Jallow.

He says a community leader from Casamance went on the radio and warned farmers not to go into their fields for fear of more violence.

"It is calm now, but the people are quite afraid, because the area isn't safe for the farmers, because they, the rebels, have buried land mines everywhere," added Jallow.

Upsurge in armed attacks has become a regular occurrence during cashew-nut harvest time.

A peace accord between the Senegalese government and a main rebel group was signed in 2004, but attacks on government officials have continued. Civilians are often maimed by land mines, which litter one of Senegal's most agriculturally-rich but impoverished regions.

Journalists who have followed the Casamance conflict closely say this is the first known case of deliberate mutilation during the region's 26 years of conflict.