The governor of Oio region, Secuna Baio, told the agency the firefights were worrying Guinea-Bissau's army brass and had led to "big military movements" in the area, located some 140 kilometres (85 miles) north of the capital Bissau.

Baio said sporadic small arms fire had been heard in the region throughout much of the past week.

A military source meanwhile told Lusa the army was planning to set up a field hospital in the town of Farim which is located near the border with Senegal.

The firefights between Guinea-Bissau troops and presumed rebels from the Casamance Democratic Forces Movement (MFDC), who are fighting Senegal for their region's independence, were first reported Tuesday.

Lusa said a senior officer in Guinea-Bissau had denied reports that troops from the former Portuguese colony had either been killed or injured in the border firefights.

Four troops were killed and about a dozen were injured in the skirmishes, according to sources close to their families cited on Sunday.

Casamance, once a former tourist hotspot, has been plagued by low-intensity conflict between rebels and government forces since 1982.

The largely Christian and animist region is nearly cut off from the rest of mostly Muslim Senegal by Gambia.

MFDC seperatist rebels have often sought refuge in neighbouring Guinea-Bissau.

WAR.WIRE