GOMA, Congo (AP) — Congolese soldiers and rebel forces suffered heavy casualties Sunday as they fought for a fifth day near the city of Goma in the country's volatile east, a doctor near the front line said.

Dr. Isaac Warwanamiza told The Associated Press he had seen 82 dead since early Sunday, 23 of whom were government soldiers, the highest death toll reported since hostilities broke out last week.

Medical services were struggling to cope with the scale of the casualties among government troops and the M23 fighters who launched their rebellion last year, Warwanamiza said.

"I'm overwhelmed by what I've seen: bodies blown apart, arms and feet here and there," he said, speaking by phone from a hospital north of Goma.

Three U.N. peacekeepers were wounded Saturday in the fighting, though no injuries were immediately reported by the U.N. peacekeeping mission Sunday.

A U.N. official, who spoke on condition of anonymity because he was not authorized to speak to journalists, said that two M23 "colonels" had been killed since Wednesday, while the Congolese military had not lost any senior officers.

The front line is only 9 miles (15 kilometers) north of Goma. M23 rebels briefly overtook the city late last year, and Congolese and U.N. troops have been battling to dislodge rebels from heights overlooking the city since Wednesday.

Observers estimate that Congolese forces have advanced less than a mile (about 2 kilometers) since Wednesday and have yet to achieve their immediate objective — cutting off M23 from a border crossing where the rebel group is believed to get supplies from neighboring Rwanda.

An army chaplain at the military hospital in Goma confirmed that Congolese troops had suffered heavy casualties Sunday. Chaplain Lea Masika said 59 wounded had been brought into the hospital since Sunday morning, bringing the total of wounded there to 720. The bodies of three Congolese officers had been buried, he said.

The M23 is made up of hundreds of Congolese soldiers mostly from the Tutsi ethnic group who deserted the national army last year after accusing the government of failing to honor the terms of a deal signed in March 2009. Many of the movement's commanders are veterans of previous rebellions backed by Rwanda, which vigorously denies allegations that it has been supporting and reinforcing M23.

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The rebels briefly seized Goma, a city of nearly 1 million people, last November, before withdrawing under international pressure and in return for a promise of peace talks with the government. The talks in neighboring Uganda have frequently stalled and appear to have made little progress since March.

The renewed fighting erupted Wednesday, breaking a three-week lull in the region. On Thursday, the new U.N. intervention brigade that was created in March with a strong mandate to protect civilians fired for the first time on rebel positions.

"We are using artillery, indirect fire with mortars and our aviation, and at the moment we have troops in the front line alongside (the government forces)," Gen. Dos Santos Cruz, the U.N. force commander in Congo, said Saturday.

In Washington, the state department condemned the actions of the M23, voicing concern over "credible U.N. reports that the M23 has fired into Rwandan territory." In a statement issued Sunday, it called on the rebel group to immediately cease hostilities, disarm and disband.

There has been widespread skepticism, however, in Congo that the intervention brigade will be a game-changing addition to the existing U.N. force, which stood by when M23 fighters captured Goma late last year.

On Saturday, scores of Goma residents took to the streets in anger over a series of rocket and mortar attacks that have left at least seven civilians dead in recent days. Two other residents were killed during the demonstration, and the U.N. called for a joint investigation.