There is proof of deliberate destruction in Sudan, claims a satellite monitoring programme set up by actor George Clooney and others.
The incidents took place in the key state of Southern Kordofan, an oil-rich region, where a hotly contested election for governor is under way.
The Satellite Sentinel Project says around 356 buildings have been burnt in the town of El Faid.
According to reports, more than 20 people have been killed in fighting.
The lack of scorching between buildings in the town suggests the burning was deliberate, the Satellite Sentinel Project says.
El Faid is the hometown of Abdelaziz al Hilu, one of the leading candidates in Southern Kordofan's governorship election.
Mr Hilu claims militias loyal to President al-Bashir attacked El Faid, but President Bashir's party denies this.
The state is next to the disputed region of Abyei and borders South Sudan, which will become independent in July.
In the Nuba Mountains inside Southern Kordofan, there are many thousands of people who fought with the southern rebels against Khartoum.
They are expected to vote for Mr Hilu.
But it is difficult to see how President Bashir's party could accept losing the poll in such a vital area.
Its candidate and current governor Ahmed Haroun is wanted by the International Criminal Court for crimes allegedly committed in Darfur.
The vote will take place at the beginning of May.