Separatist rebels from Senegal's southern Casamance region have clashed with troops from Guinea-Bissau along the border between the two countries.
The splinter group rejects the 2004 peace deal
At least two Guinea-Bissau soldiers have been killed since attacks began on Tuesday this week.
Clashes were reported on both sides of the border, involving rival factions of rebels as well as Guinea-Bissau troops.
The main Casamance rebel movement has signed a peace deal with Senegal's government, which hardliners reject.
The hardline wing of the Casamance Movement of Democratic Forces (MFDC), led by Salif Sadio, opposes the 2004 agreement and continues to campaign for the independence of Casamance.
Fighters from the main group attacked positions held by the hardliners near Kassorol on Tuesday night and Wednesday, security sources in Casamance told Reuters news agency.
Guinea-Bissau troops later repulsed fighters from an MFDC faction who were trying to buy weapons in the Guinea-Bissau town of Sao Domingos, military sources told AFP news agency.
This week's incidents along the border represent the most serious violence since the peace deal was signed just over a year ago.
Casamance is struggling to rebuild itself following the violent separatist rebellion that lasted more than 20 years and killed an estimated 3,500 people.