Fighting flared again on the border of Rwanda and the Democratic Republic of Congo early on Thursday, the second day of skirmishes between two neighbours locked in a decades-long dispute.
Rwandan and Congolese troops traded heavy weapons fire around 0600 GMT, said one witness.
"There were heavy arms fire explosions, rockets," the resident told AFP on condition of anonymity.
A senior Congolese military officer said that Rwandan troops "attacked our positions."
A Rwandan military source, also speaking anonymously, told AFP that there had "not been serious clashes, they were sporadic firings" of heavy weapons.
The fighting came a day after the two sides exchanged gunfire on Wednesday, with each blaming the other for the outbreak of violence.
The Congolese army said the fighting started after the abduction of one of its soldiers by Rwandan troops who had crossed the border into the restive North Kivu region, while Rwanda said Congolese troops crossed into its territory and opened fire on Rwandan soldiers.
The two country have long been at odds, with Rwanda repeatedly accused by the United Nations and its neighbour of backing a rebellion by the M23 rebel group that temporarily seized control of parts of eastern DRC.
Rwanda last year accused the Congolese army of firing rockets and mortar shells on its territory, and massed troops along its border in response.
Rwanda backed Tutsi-dominated militias rebel groups fighting the Kinshasa government during Congo's civil wars in 1996-97 and 1998-2003, and has been involved in several attempts to destabilise the country by supporting Tutsi-dominated militias.
There are fears the latest violence could undermine international efforts to bring stability to the DRC's lawless east after years of bloody conflict.
The conflict is fuelled by the east's wealth of mineral reserves -- particularly gold and minerals used in electronic products.
Wednesday's clashes took place around 20 kilometres (12 miles) northeast of Goma, capital of troubled North Kivu province, where rebels from a Hutu group linked to the 1994 Rwandan genocide began surrendering last month.
The rebels are members of the Democratic Forces for the Liberation of Rwanda (FDLR), which includes remnants of the militia that carried out the genocide of at least 800,000 ethnic Tutsis.
The FDLR has around 1,500 men, according to UN estimates, or 4,000, according to Kigali. They have been accused of widespread violence and rights abuses in the DRC.
Western officials sought to play down the escalating rhetoric on Wednesday, as Rwandan Foreign Minister Louise Mushikiwabo said the country stood "ready to act to protect its citizens" against further attacks.
"We are in contact with both governments and are trying to understand exactly what happened... This is to reduce the tension," a senior United Nations official told AFP.
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Rwanda, DR Congo trade blame for heavy border fighting