GOMA, DR Congo / UNITED NATIONS - Rebels of the March 23 Movement (M23) on Monday took control of the facilities of the Congolese National Radio and Television (RTNC) in Goma, a city under onslaught by the rebel group in eastern Democratic Republic of the Congo (DRC), sources of RTNC confirmed.

Radio Okapi, a media outlet supported by the United Nations Stabilization Mission in the DRC, cited multiple sources and described the siege of the national television station as a strategic advance for the rebels, who are seeking to establish their domination over the city.

Since Sunday evening, gunfire has been heard across Goma. On Monday morning, fighting intensified in various parts of the city, including areas near the border with Rwanda, local sources told Xinhua.

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Other local sources said that the rebels gained the upper hand after capturing Mount Goma, a strategic hill 1,500 meters above sea level in the city's center.

Several M23 columns entered neighborhoods in the city, with their movement along both major and minor roads observed by residents.

According to UN sources, the border between Rwanda and the DRC near Goma was closed Monday morning. For several days, a significant number of Goma residents have crossed the border to seek refuge in Gisenyi, a Rwandan town bordering the DRC, where panic has been mounting amid reports of gunfire.

In its latest statement released early Monday, the M23 announced that the "liberation of the city has been completed" and that "the situation is under control" following a 48-hour ultimatum given to Congolese soldiers.

On Saturday, the M23 issued a 48-hour deadline for the DRC armed forces and their allies to surrender.

The DRC government said Monday that it "continues to work to avoid carnage and the loss of human life" in Goma. Meanwhile, DRC President Felix Tshisekedi called an inter-institutional meeting in Kinshasa, the capital of the DRC, but his spokesperson Tina Salama did not give further details.

Tensions remain high following recent advances by the M23 in North Kivu and South Kivu provinces.

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According to sources of the UN peacekeeping mission, several important facilities have been taken over by the rebel group, including the airport, the port and a local base of the DRC military. The latest report from a UN group of experts said the rebels have seized several towns and established a parallel administration.

UN urges ceasefire

The United Nations Security Council Sunday night condemned strongly ongoing advances by the M23 rebels in the eastern Democratic Republic of the Congo (DRC), demanding them withdraw immediately and urging all parties to abide by the ceasefire.

In a press statement issued after an emergency meeting on the DRC, the council members condemned the M23 in North-Kivu province, and expressed serious concerns regarding imminent threats against Goma, the capital of North Kivu and a major regional hub.

These advances "represent a serious violation of the ceasefire, exacerbate the grave humanitarian and displacement crisis in the eastern DRC and undermine efforts to reach a lasting peaceful and political solution to the conflict through the Luanda process," the statement said.

The council members demanded that the offensive and advances towards Goma immediately stop, calling on the M23 to reverse its territorial expansion without delay.

READ MORE: UN: M23 renewed fighting near key town in eastern DRC

They reiterated their full support to the United Nations Organization Stabilization Mission in the Democratic Republic of the Congo (MONUSCO), which is acting within its mandate and doing essential work in the DRC, and expressed their strong commitment to the safety and security of its peacekeepers.

They stressed that attacks against peacekeepers may constitute war crimes. The council members condemned the ongoing flagrant disregard for the sovereignty and territorial integrity of the DRC, and demanded the external forces in the eastern country withdraw immediately.

They urged all parties to scrupulously abide by the ceasefire. They urged Rwanda and the DRC to return to diplomatic talks to achieve a lasting and peaceful resolution of the protracted conflict in the region, and reaffirmed their support for the ongoing mediation efforts between the two countries through the Luanda Process.

As the situation is deteriorating rapidly in the eastern DRC, several foreign embassies have issued advisories urging their citizens to leave North Kivu.

The United Nations announced Saturday that it has temporarily relocated non-essential staff from Goma.