GOMA, Democratic Republic of Congo (Reuters) - Six Congolese soldiers were killed, a senior army officer said on Friday, in a clash with Rwandan forces this week that now risks inflaming tensions between two neighbors with a long history of troubled relations.

The two countries dispute which side of the poorly demarcated border the clash took place on, each accusing the other’s forces of violating the frontier. They have called upon the ICGLR, a body representing regional governments, to visit the scene of Tuesday’s clash to investigate.

General Bruno Mandevu, an operational commander in eastern Democratic Republic of Congo, said six soldiers died in the incident, up from an earlier figure of five. Six other soldiers were wounded, two of them seriously, he said.

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“In the beginning, we thought they (the attackers) were an armed group, particularly M23. Thanks to our technological tools, notably GPS, our Congolese soldiers found the location and the enemy fled toward Rwanda,” Mandevu told a news conference.

Rwanda’s army spokesman was not immediately available to comment on possible Rwandan casualties during the clash.

M23 were one of a series of Congolese rebel groups that U.N. investigators blamed Rwanda for supporting in the wake of two major wars in Congo from 1996-2003 during which Rwandan troops invaded Congolese territory.

Rwanda has denied supporting insurgents in Congo.

M23 were defeated by Congolese troops and U.N. peacekeepers in 2013 and hundreds of the group’s fighters fled into Rwanda and Uganda.

Writing to the ICGLR on Wednesday, Rwanda’s army said that Congolese troops “violated our territorial border and subsequently attacked our defensive position”.

Mandevu said the fighting occurred inside Congo’s Virunga National Park. He said it began around 8 a.m. (0600 GMT) on Tuesday and ended six hours later after the heads of the Congolese and Rwandan armies declared a ceasefire.

Militia and rebel attacks are on the rise in Congo, particularly in the restive eastern borderlands.

More than 4.4 million people have been displaced across the vast Central African nation amid rampant violence that has been aggravated by a political crisis sparked by President Joseph Kabila’s refusal to step down at the end of his mandate in 2016.