NAIROBI, Kenya (AP) — U.S. Secretary of State Antony Blinken has urged Rwanda and Congo to de-escalate tensions and withdraw troops from their border following increased fighting that has displaced nearly 7 million people.

Blinken spoke separately by phone with Congolese President Felix Tshisekedi and Rwandan President Paul Kagame about the “volatile situation and worsening humanitarian crisis along the border,” the State Department said.

Its statement said Blinken advocated for a diplomatic solution to the tensions.

Fighting between M23 rebels and militias loyal to the Congolese army has intensified in the eastern Congo provinces of Ituri, North and South Kivu and Tanganyika.

The Congolese government has repeatedly accused Rwanda of supporting the M23 rebels who have taken control over swathes of territory in eastern Congo. U.N. experts have said they had strong evidence that Rwanda’s army was fighting alongside the rebel group. Rwanda has rejected the accusations and instead accused Congo’s army of shelling villages in Rwandan territory along the border.

The International Organization for Migration has described the situation as the largest internal displacement and humanitarian crisis in the world.

Thousands of civilians have been killed. Millions have been displaced internally. Hundreds of thousands have fled into neighboring Uganda.

“For decades, the Congolese people have been living through a storm of crises,” Fabien Sambussy, IOM’s chief of mission in Congo, said earlier. “The most recent escalation of the conflict has uprooted more people in less time like rarely seen before.”

Congo is expected to hold presidential elections next month, but there are concerns that the escalation of violence in the east will affect the polls in which Tshisekedi seeks another term.