The Rwandan army says several civilians have been injured in cross-border shelling by troops from the Democratic Republic of Congo.
It said it had asked a regional team of military observers, the Expanded Joint Verification Mechanism, to conduct an urgent investigation.
Tensions between the two countries have increased since March, when the M23 rebel group attacked two Congolese army positions.
Rwanda denies accusations that it supports the rebels.
The group seized territory in eastern DR Congo during an insurrection in 2012 and 2013, before its fighters were driven out by Congolese and UN forces.
Many families have left their homes in DR Congo’s North-Kivu province, heading for the Ugandan border town of Bunagana.
The head of the UN Refugee agency in Uganda, Joel Boutroue, told the BBC several thousand refugees arrived in Uganda on Monday.