Intense South Sudan Battles Creating 'Alarming' Aid Conditions

South Sudanese government tanks backed by helicopter gunships have pushed back rebels from a key oil town, state television showed Friday, as aid agencies warned of "alarming" and worsening conditions.

Tanks are shown firing as a helicopter gunship -- believed to belong to the Ugandan army which is fighting alongside government troops -- swoops over the burning town of Melut in the key northern oil state of Upper Nile.

Doctors Without Borders (MSF) on Friday warned there was an "escalating and continued use of violence against civilians" in the three battleground northern and eastern states of Unity, Upper Nile and Jonglei.

Fighting broke out in December 2013 when South Sudan's President Salva Kiir accused his former deputy Riek Machar of attempting a coup, setting off a cycle of retaliatory killings across the country.

Footage from the recent battle, filmed earlier this week, show men with rocket-propelled grenades crowded onto pickup trucks, cheering as they fire heavy machine guns fixed to the back.

Melut lies some 35 kilometers (20 miles) west of the main oil production base at Palouch, which rebels are trying to capture. Its loss would be a crippling blow to South Sudan's already struggling economy.

At least three heavily armored barges, equipped with anti-aircraft guns, and used for transporting troops along the Nile river, are seen on fire, as soldiers on the river bank rake it with gunfire and rockets.

The government assault that began in late April is one of the heaviest offensives in the 17-month long civil war and has cut off over 650,000 people from aid, with gunmen raping, torching towns and looting relief supplies, according to the United Nations and aid agencies.

Rebels last week launched a major counter-attack, including an assault on Malakal, the state capital of Upper Nile and the gateway to the country's last remaining major oil fields.

MSF has been forced to abandon its hospital in the town of Leer, in southern Unity State, and pull back into U.N. bases in Malakal and Melut.

In Jonglei, an MSF team discovered the town of New Fangak "had effectively been destroyed, with trees and homes burnt to the ground and school buildings flattened," the mission's chief Paul Critchley said.

"The hospital, one of the main health facilities in the northern part of the state, had been demolished."