Sudan’s Rapid Support Forces seized the country’s largest oil field Monday, according to paramilitary, army and industry sources, as fighting escalates in the strategic, resource-rich south.

Since ousting the army from its last Darfur stronghold in late October, the RSF has turned its attention to neighboring Kordofan.

Last week, a drone strike on a kindergarten and hospital killed 114 people, including 63 children, the World Health Organization reported.

“The liberation of the Heglig oil region marks a pivotal step in the liberation of the entire homeland, given the area’s economic significance,” the RSF said in a statement Monday.

An RSF source told Agence France-Presse (AFP) that the base housing the local army division also had fallen.