The United States and European powers called Tuesday on Rwanda's military and associated M23 fighters to immediately halt an offensive in the eastern Democratic Republic of Congo, days after the countries' presidents signed an agreement in Washington.

The group led by the United States voiced"profound concern" about the violence near Burundi and said it had "a destabilising potential for the whole region".

A joint statement said the coalition"urges the M23 and the Rwanda Defense Force (RDF) to immediately halt their offensive operations in eastern DRC, in particular in South Kivu, and calls on the RDF to withdraw from eastern DRC".

The statement issued by the US State Department also calls on the M23"to return to its positions and uphold... commitments of the Declaration of Principles" reached in negotiations with the Kinshasa government held in Qatar in July.

Also signing the statement were the European Union and former colonial power Belgium, as well as the UK, Denmark, France, Germany, the Netherlands, Sweden and Switzerland.

Just hours later, M23 fighters entered DRC's key eastern city of Uvira, souces said, with thousands fleeing across the border into Burundi to escape the militia's latest advance.

According to military and security sources, the militia's fighters entered the strategic border town at the gates of Burundi from the north.

The Rwandan and DRC presidents had signed an agreement on Thursday in Washington in the presence of US President Donald Trump, who boasted of his credentials as a peacemaker.

But both the DRC and neighboring Burundi have voiced alarm in the days since then as the Rwandan-backed M23 has attacked border areas.

The group statement also expressed"particular concern at the increased use of both attack and suicide drones in the conflict".

"This represents a significant escalation in the fighting and poses an acute risk to civilian populations," it said.