Rebels in Congo have surrounded the eastern city of Goma, in one of the sharpest escalations in years of a conflict that has pitted the Central African country against its neighbor Rwanda.

Rwanda-backed M23 rebels in the Democratic Republic of Congo have taken over the key eastern trading town of Minova, according to various sources. The fall of the city puts the rebels within 40km (25 miles) of provincial capital, Goma, which lies close to the border with Rwanda.

The M23 rebel group’s advance toward eastern Congo’s largest city has displaced over 178,000 people in the past two weeks, the United Nations said, as the fighters closed in on Goma on the border with Rwanda.