The latest attacks in north Darfur killed a government soldier and an unknown number of rebels on Friday, the Sudanese military said.
"A group of rebels ... on about nine vehicles ambushed an administrative patrol Friday," said Sudanese army brigadier Osman Al-Aghbash.
"A soldier was martyred and another wounded in the fighting," he said.
On Friday, the Justice and Equality Movement (JEM), an armed Darfuri opposition movement which did not sign the peace deal in May, had accused the government in Khartoum of attacking rebel bases.
The JEM said the government, supported by its Janajaweed militia, had shelled the area of Kulkul, about 35 kilometres (22 miles) from North Darfur's capital Al-Fasher and launched numerous air attacks.
"The battle is still continuing," said Izz Al-Din Yusuf, a local JEM fighter, warning that the group would retaliate.
"We will enter Al-Fasher and occupy the airport if the government continues shelling them by planes," Yusuf said, warning citizens to evacuate the area.
The JEM says that the government was attempting to punish groups who had not supported the peace agreement which Khartoum signed with Darfur’s main opposition group, the Sudan Liberation Movement (SLM) in Nigeria on May 5,
"The Khartoum regime has begun implementing a military project that aims at an all-out assault on the parties which did not sign the farcical Abuja 'agreement'," JEM spokesman Ahmed Hussein Adam said.
The United Nations and African Union peace-keeping missions in Sudan denounced Sudan’s attack on the JEM, saying they were "deeply concerned about the fighting."
The JEM spokesman said Khartoum was planning more attacks and had mobilised "some 400 Janjaweed on horses and camels with full armament and logistic support, including 82 vehicles."
Under the terms of the May peace agreement, Sudan had promised to disarm the Janjaweed militia which is accused of raping and murdering thousands of Darfuri civilians.
Over 2 million civilians have been displaced by fighting in Darfur
A smaller faction of the SLM and the JEM had rejected the peace deal in May, saying it did not meet their demands and provided no safeguards to ensure that Sudan would not renege on its promise to disband the Janjaweed.
The Sudanese government has denied using aircraft or the Janjaweed in the latest violence.
Since 2003 fighting in Darfur has killed at least 300,000 people – most of them civilians – and displaced 2.4 million more.
The violence began when inhabitants of Darfur protested against what they saw as systematic under-funding and under-development of their region by Sudan’s Arab, Islamist government in Khartoum.
The leader of the Sudan People's Liberation Movement (SPLM), south Sudan’s main secessionist movement, has meanwhile accused Sudan’s government of continuing to arm and support militias in the south.
"The continuation of support to militias in the south from elements of the Sudanese Armed Forces (SAF) is a violation of the peace agreement," said Pagan Amum, secretary general of the SPLM.
The 2005 peace agreement that ended the war between mainly Christian south Sudanese tribes and the Islamic government in Khartoum specified that Sudan must not arm rival tribes in the region.
However since the peace treaty was signed, continuing violence in southern Sudan has killed hundreds, leading separatist groups to claim that pro-Khartoum tribes are still being supplied by the government.
"It is known who is giving them arms, it is known who is giving them money ... elements from SAF are continuing to arm them," Amum said.
There are 10,000 United Nations troops deployed in southern Sudan but they have been largely unable to stop the sporadic violence which has mainly taken place around the Upper Nile region and near Sudan’s main oil fields.