Government troops and Arab militias have attacked Massaleit, Fur, Zaghawa and other "black African groups", a Massaleit group in exile said on Tuesday.
At least 80 people from these tribes were killed and scores of villages were destroyed in recent attacks on towns and villages in North darfur state, the statement said.
It added at least 2,000 people fled the attacks into neighbouring Chad.
The group said the atrocities are in revenge for the tribes' support for the rebel Sudan Liberation Army, which briefly occupied the western Kutuum area earlier this month.
It urged human rights organisations and foreign governments to press Khartoum to "end the atrocities" in western Sudan.
No independent confirmation of the attacks was possible.
Sudan has been wracked by civil war for the past 20 years.
Accusations of atrocities and human rights abuses are frequently levelled by both Khartoum's Islamist government and rebels.