MALAKAL, South Sudan -- This used to be South Sudan's second largest city, a bustling centre on the White Nile River of more than 120,000 people, many employed in the oil fields nearby.

Today Malakal is rubble and almost entirely deserted by civilians, a city emptied by three years of civil war and now by new rounds of fighting. Following clashes in the city's outskirts last week, the army flew in journalists to show that the government retains control of the strategic city, even though rebels still vow to take it.

The army said 56 rebels and four government soldiers were killed in the fighting.

Racing through the city on the back of a pickup truck and traversing the Nile with amphibious vehicles, the soldiers still exhibited a battle high.

"I want to kill," one soldier snarled, approaching the scene of the fighting.

Many identified the corpses of rebel fighters by their ethnicity.

"Nuer, Nuer," one soldier said, pointing at bodies he said were from the Nuer tribe among the dozens scattered in a burned field. South Sudan's second largest group, the Nuer, largely follow rebel leader Riek Machar, who is now in exile but vows to return.

"Shilluk," said another soldier pointing to a nearby body, calling out another ethnic group.

The soldiers' identification of the corpses by their ethnicity is an indication that South Sudan's current conflict continues to be fueled by tribal differences. Fears grow that this East African nation is on the brink of another catastrophic outbreak of violence between President Salva Kiir and rebel leader Machar, more than a year after a peace deal that has been violated repeatedly by fighting.

Standing in a burnt field, army spokesman Lul Ruai Koang urged journalists to take photos of fighters' bloated corpses.

He emphasized that the rebels had attacked army positions, justifying the deadly response.

"We have not violated the permanent cease-fire," Koang said, adding that the location of the bodies near army positions proved that the army had been fighting in self-defence.

South Sudan's peace deal, signed in August 2015, was supposed to end the country's civil war that began in December 2013 and killed tens of thousands. But the agreement was never fully implemented, and now it is rapidly crumbling.

Hundreds of civilians died in July after clashes broke out in the capital, Juba, and fighting has again spread to many parts of the country.

A rise in ethnic tensions began after the July fighting, which saw ethnically targeted killings, according to a recent U.N. panel of experts report.

Kiir is largely supported by the Dinka, the largest of South Sudan's more than 40 tribes.

There are important exceptions to South Sudan's tribal narrative. A handful of prominent figures in the government are Nuer and Equatorian, and some figures in the opposition are Dinka. Fighting in some areas of South Sudan is mainly driven by local disputes, not tribalism.

In public, Kiir has urged reconciliation and fought against the ethnic tensions, saying in a recent speech that he cannot "become a tribal leader."