A shaft collapsed at the country's largest coltan mine in the rebel-controlled east on Tuesday, witnesses told AFP, with an initial toll of six dead.

The Rubaya mining site lies about 70 kilometres (45 miles) west of Goma, capital of North Kivu province, which is under the control of the Rwanda-backed armed group M23.

"The provisional toll counts more than 200 compatriots who lost their lives, including 70 children and numerous wounded," said the mining ministry in a statement.

AFP could not independently confirm the toll in the remote region, where neither humanitarian organisations nor major health structures have access and where telecommunications are regularly cut.