Nine Chinese mine workers were killed in an attack in the Central African Republic, sparking a rare call on Monday from China’s President Xi Jinping for the perpetrators to be “severely” punished.

The attack by “armed men” happened at about 5:00 am near Bambari, said the central town’s mayor Abel Matchipata.

Matchipata told AFP that “nine bodies and two wounded” had been counted, adding that the victims were Chinese workers at a site run by the Gold Coast Group, 25 kilometres (15 miles) from his town.

The president had ordered “an all-out effort to treat the wounded, handle the aftermath in a timely manner, severely punish perpetrators in accordance with the law, and ensure the safety of Chinese citizens”, an unnamed China foreign ministry spokesperson said in a statement.

Local authorities did not release further details of the attack, nor was there any claim of responsibility.

China and Russia are bolstering their presence in Africa to tap its rich natural resources, analysts say, despite grave warnings from UN agencies that the world’s poorest countries face accumulating crippling debts

“One out of every three major infrastructure projects in Africa is built by Chinese state-owned enterprises, and one out of every five is financed by a Chinese policy bank,” Paul Nantulya of the Africa Center for Strategic Studies, an academic institution within the US Department of Defense, told AFP.