NAIROBI, Kenya — Sudan’s armed forces have launched a major offensive in northern Darfur, where China wants to explore for oil, rebel commanders said yesterday.

Soldiers in a convoy of more than 200 vehicles stormed two rebel strongholds close to the Sudan-Libya border in an attempt to wrest territorial control from forces opposed to the regime in Khartoum.

The attacks on Tuesday were the first in Darfur by the government since the International Criminal Court prosecutor charged President al-Bashir with war crimes and genocide last month.

A rebel leader claimed that the government had taken Chinese oil engineers to the area recently, to join Saudi teams already licensed to search for new deposits.

Sudanese state officials denied that there was any exploration in the area.

At least seven rebels were killed in Tuesday’s offensive, said Suleiman Marajan, a Darfur-based commander of the faction of the Sudan Liberation Army led by Abdel Wahed Mohamed el-Nur.

Government forces were said yesterday to be moving further north to continue efforts to beat back the rebels.

“They are readying to move to other places. … The government is cheating us and cheating the international community. They are going to destroy all the places to control them,” Mr. Marajan said.

A second commander from the same rebel faction, Ibarahim al-Hillo, called the government offensive a “second round of ethnic cleansing.”

A spokesman for the other rebel group targeted in the raid, the rival Sudan Liberation Army (Unity), said the army attacked “with a massive force” close to Wadi Atron. “We consider this a new declaration of war,” said al-Sayyid Sherif.

The area is part of a vast oil exploration concession known as Block 12A, currently under licence to al-Qahtani, a Saudi Arabian firm.

China is Sudan’s largest crude customer, buying 60% of its oil.