Updated

A rebel group created just seven months ago attacked the strategic provincial capital of Goma, home to more than 1 million people in eastern Congo, on Tuesday, seizing part of the city and the international airport, according to a rebel spokesman, residents and eyewitnesses.

Explosions and machine-gun fire rocked the lakeside city as the M23 rebels appeared to push forward on two fronts: toward the city center and along the road that leads to Bukavu, another provincial capital which lies to the south. The rebels are allegedly backed by neighboring Rwanda, which the Rwandan government denies.

"We already took the airport and part of the city," said rebel spokesman Col. Vianney Kazarama, reached by telephone on Tuesday. "We are now inside the city of Goma."

An official at the United Nations peacekeeping base in Goma, who requested anonymity because she was not authorized to speak to the press, confirmed that the airport had fallen. A factory owner whose business faces the airport said he saw the rebels go onto the tarmac. By late Tuesday morning, he said that the shooting had stopped there and that the airport appeared quiet.

Goma was last threatened by rebels in 2008 when fighters stopped just short of Goma. The United Nations has said that if Goma were to fall, a humanitarian catastrophe would result. The rebels, believed to be backed by Rwanda, have been fighting Congolese government forces which are backed by U.N. peacekeepers, tasked with protecting civilians.

But Congolese military spokesman Olivier Hamuli said that the U.N. peacekeepers, known by their acronym MONUSCO, were not helping the government forces during Tuesday's battle because they do not have a mandate to engage the rebels.

"MONUSCO is keeping its defensive positions. They do not have the mandate to fight the M23. Unfortunately, the M23 did not obey the MONUSCO warnings and went past their positions (at the airport). We ask that the MONUSCO do more," he said.

Germany, which is a member of the U.N. Security Council, called on the rebels to halt their military action immediately. Foreign Minister Guido Westerwelle said in a statement that he called on Congo's neighbors, a reference to Rwanda and Uganda which are accused of backing M23, to not do anything to worsen the crisis. "I expect of Congo's neighboring states that they refrain from doing anything which further exacerbates the situation," Westerwelle said.

If the rebels succeed in taking Bukavu, the capital of South Kivu province, it will mark the biggest gain in rebel territory since at least 2003, when Congo's last war with its neighbors ended. The M23 rebel movement started in April, and is led by soldiers who defected from the country's army. They are nearly all from the Tutsi ethnic group, the same ethnicity that was targeted during the 1994 genocide in neighboring Rwanda.

They claim that they are fighting for their community but several, in-depth investigations by the United Nations Group of Experts has shown that M23 is being propped up by Rwanda, and is more likely linked to the fight to control eastern Congo's rich mineral wealth. The provinces of North Kivu, where Goma is located, and South Kivu contain one of the highest concentrations of tin, tantalum and tungsten mines, minerals that are used in computers, mobile phones and digital cameras.

Fidel Bafilemba, a researcher for the Washington-based Enough Project who lives near the road to Sake, the first town on the drive to Bukavu, said: "The road to Sake seems to be controlled by the M23. A lot of people are fleeing toward the center of town, carrying mattresses, belongings on their heads."

Another resident living near the strategic road, Jean-Claude Bampa, spoke on the telephone over loud gunfire in the background. "I can hear gunshots everywhere, it is all around my home," he said on Tuesday morning.. "We are stuck inside and are terrified. I pray this will be over soon."