South Sudan's army is steadily capturing more rebel-held territory, even as peace talks try to find a resolution to the country's nearly four-year-old civil war.

As the army gains ground, complaints are growing that both sides are committing atrocities against civilians.

The Associated Press recently spoke with eight rebel soldiers who had been on the front lines in a rebel-held area and all recounted similar events: government forces gang-raping women, burning houses with people inside and killing children.

Inconclusive peace talks were held in the capital, Juba in October. The negotiations are scheduled to resume in December and by that time opposition forces probably will have lost more territory, experts say.

In the last six months, despite President Salva Kiir's declaration of a unilateral cease-fire, government troops have captured large swaths of land previously held by rebel forces. What was once the opposition heartland, Upper Nile state, is now mostly under government control.

South Sudan's civil war has killed tens of thousands and forced more than two million people to flee the country, creating the largest displacement of civilians in Africa since the Rwanda genocide in 1994. Refugees, and some of the more than 200,000 people sheltering in United Nations-run camps across South Sudan, have recounted targeted killings and rapes by government troops.

In the Equatoria region, Amnesty International found many accounts of civilians being killed with "reckless abandon" by government forces and allied militia, according to a report issued in July.

South Sudan's army has denied the allegations, saying the opposition is spreading "negative propaganda" in order to portray them as "butchers."

"This is what you'd expect from your opponent," said acting army spokesman Col. Santo Domic Chol. "We don't kill women and children and we don't want to kill everybody in South Sudan."

The government's purpose is to promote peace and have everyone, including the opposition, join in national reconciliation, Chol said.

The South Sudan government's campaign is pushing the rebels further into the bush rather than "convincing them to give up arms," said Alan Boswell, conflict analyst for Small Arms Survey, a Geneva-based group focusing on armed violence. "The government hopes to dictate victory on its own terms rather than being forced into a political settlement with its opponents."

With the dry season approaching and fighting expected to increase, rights groups are urging both sides to stop the attacks, including violence against civilians, said Jehanne Henry senior Africa researcher for Human Rights Watch.

"Since the start of the conflict we have been documenting horrific attacks on civilians and it's high time government puts an end to these crimes and holds those responsible to account," Henry said.

Justin Nyuol, chairman of South Sudan's Human Rights Commission, agreed.

"While it's true some government forces have committed atrocities, opposition fighters have committed atrocities as well, including in Equatoria or other areas where they control, Nyuol said.

"There is an element of brutality and it's being carried out by all the parties to the conflict. ... When the war gets more intense the level of brutality goes up."