Members of South Sudan's former rebel army, the Sudan People's Liberation Army (SPLA), are seen in the town of Bentiu, on January 12, 2014
Juba (AFP) - South Sudan's civil war entered its ninth month Friday with rebels and government troops engaged in heavy battles, both sides said, days after UN warnings of sanctions over the conflict.
Fighting was reported around the town of Bentiu, capital of the northern oil state of Unity, as well as in the Ayod region of Jonglei state, with each two side accusing the other of launching attacks.
Rebel spokesman Lul Ruai Koang claimed it was the start of a "long-awaited government offensive."
Army spokesman Joseph Marier Samuel said troops had acted in "self-defence", accusing the rebels of launching a dawn attack at Ayod. He claimed the rebels were repulsed with heavy casualties.
In Bentiu, fighting was reported to have continued for several hours, including around the key airport zone outside the town, close to the UN base.
"It is a continuous violation of the ceasefire agreement," Samuel said.
Aid workers reported heavy shooting around Bentiu, which has changed hands between rebels and government troops several times since fighting first broke out in December.
"We heard heavy shelling erupting early this morning," said Timothy Ngyuai from the aid agency CARE, adding that they had taken initially been forced to take shelter in bunkers.
The British ambassador in Juba, Ian Hughes, said the fighting was "disappointing", coming just three days after UN Security Council envoys visiting the troubled nation warned both the government and rebel leaders of "consequences".
"The situation there is desperate enough already," Hughes said. "Leaders need to control their fighters."
- Looming famine warnings -
UN envoys met with President Salva Kiir in Juba and also spoke with rebel chief Riek Machar, urging them to stick to peace after three failed ceasefire deals.
US Ambassador to the UN Samantha Power on Tuesday cited "very worrying reports" that more weapons and arms were being brought into South Sudan for a fresh offensive.
Thousands of people have been killed and more than 1.5 million have fled civil war sparked by a power struggle between Kiir and his sacked deputy Machar, with battles between government troops, mutinous soldiers and ragtag militia forces divided by tribe.
The United Nations has said the food crisis is the "worst in the world", with aid workers warning of famine within weeks if the conflict continues.
UN aid chief in South Sudan Toby Lanzer said the fighting in Bentiu was a "stark reminder of the difficult conditions under which aid agencies and peacekeepers work".
More than 40,000 civilians are crammed into the UN base in Bentiu, flooded with heavy rains and knee-deep in raw sewage, in conditions the aid agency Doctors Without Borders (MSF) has described as "horrifying".
Over a third of residents are children younger than five. While MSF says that death rates have improved, a child is still dying in the camp each day.
Like almost 100,000 civilians in UN camps across South Sudan, the people fled to the Bentiu base in December to escape killings and massacres, and are now too fearful to return home with fighting still raging.
The United States and the European Union have already imposed penalties on three senior South Sudanese army commanders from the government and opposition, while nations in the regional bloc IGAD have suggested they could follow suit if progress was not made.
East African leaders are to hold an IGAD meeting at the weekend in the Ethiopian capital to discuss the war in South Sudan.