CAIRO (AP) — A paramilitary group in Sudan attacked a city in the western Darfur region, killing more than 30 people, an activist group said, in the latest deadly offensive on an area that is home to hundreds of thousands of displaced people.

The Rapid Support Forces, or RSF, and allied militias launched an offensive on el-Fasher, the provincial capital of North Darfur province, on Sunday, the Resistance Committees in the city said. Dozens of other people were wounded in the attack, said the group, which tracks the war.

The RSF renewed its attack on Monday, shelling residential buildings and open markets in the city, the activist group said. There was no immediate comment from the RSF.

El-Fasher, more than 800 kilometers (500 miles) southwest of the capital, Khartoum, is under the control of the military, which has fought the RSF since Sudan descended into civil war more than two years ago, killing more than than 24,000 people, according to the United Nations, though activists say the number is likely far higher.

The RSF has been attempting to seize el-Fasher for a year to complete its control of the entire Darfur region. Since then, it has launched many attacks on the city and two major famine-hit camps for displaced people on its outskirts.

The city is now estimated to be home to more than 1 million people, many of whom have been displaced by the ongoing war and previous bouts of violence in Darfur. The RSF grew out of the notorious Janjaweed militias, mobilized two decades ago by then President Omar al-Bashir against populations that identify as Central or East African in Darfur. The Janjaweed were accused of mass killings, rapes and other atrocities.

The attacks on el-Fasher have intensified in recent months as the RSF suffered battlefield setbacks in Khartoum and other urban areas in the county’s east and center.

Sunday’s violence came less than a week after a two-day attack by the RSF and its allied militias on the city and the Zamzam and Abu Shouk camps killed more than 400 people, according to the United Nations.

Last week’s attack forced up to 400,000 people to flee the Zamzam camp, Sudan’s largest, which has become inaccessible to aid workers, U.N. spokesman Stéphane Dujarric said.