Oil is changing the stakes in Sudan's civil war.

The conflict has long been seen as a battle between the Muslim government in the north and rebels in the largely Christian and Animist south. But now that oil production in southern Sudan is cranking out over 200,000 barrels a day — bringing in $500 million — it's also about money.

Critics of the Muslim-led government say oil profits are paying for the helicopters and bombers used in the war effort. And the goals of those military actions, the critics maintain, are aimed at pushing people away from the oil fields in an effort to secure them for development.

The Sudanese government practices what critics call a "scorched-earth," or low-level ethnic cleansing policy. In one area near this oil-drilling center, some 20,000 people are said to have been driven from their homes.

Sources in the south tell Fox News Sudanese government aircraft first bombed the villages here, then sent in ground troops. Fox News visited the area and found that in the town of Padiet, there was nothing more than the foundations and remains of dozens of houses and farms.

The inhabitants had long left. A local official, David Majang, charged government troops had acted "because they want the oil."

In the nearby town of Bouth, there were some 2,000 Sudanese who said they had forcibly evicted from their villages. They told tales of death and destruction.

"We're afraid," one woman said, "because the troops want to kill us and control the area."

Displaced Sudanese in the south often seek the protection of the rebel Sudan People's Liberation Army, or SPLA. While most of its members belong to the Dinka tribe, they do no claim to fight for the secession of the south, but for a secular and democratic Sudan.

Deep in the hills of southern Sudan, at his secret compound, Fox News met up with John Garang, the charismatic rebel leader who once attended Iowa State University.

"We are resisting the various attacks on us and our civil population," he said in an exclusive interview. Garang's men have scored gains in recent weeks, and claim to have struck against government-controlled oil facilities.

And more such attacks are likely.

"We will target oil companies and oil installations," he said. "Close down and get out until a final peace solution is worked out," he warned the oil companies who have contracted with the Sudanese.

Citing reports of human rights abuses, the U.S. Congress has sent a message of its own. The Sudan Peace Act, passed by the House of Representatives, calls for restrictions on any firms doing oil business with Sudan.

For their part, Sudanese government officials insist oil revenues benefit the entire country, north and south. They also deny charges the government is clearing out villages near the oil fields or using the money to bulk up the military.

"We have nothing to hide," Khidir Haroun Ahmed, the Sudanese Charge d'Affaires, told Fox News. "It is quite clear that all these charges are based on propaganda."

Still, with billions of barrels of oil in potential reserves in Sudan there is little chance the government will give in to all the rebel demands - which include self-determination in the south, and a major share of that oil.

If anything keeps the bloody civil war in Sudan raging, it will be this new source of wealth - and, it is claimed - terror.

Greg Palkot currently serves as a London-based senior foreign affairs correspondent for Fox News Channel (FNC). He joined the network in 1998 as a correspondent. Follow him on Twitter@GregPalkot.