GENEVA (AP) — Congo's justice minister says investigations into killings in the central Kasai regions have "progressed well" and four people have been arrested over the grisly slayings of two U.N. experts.

Alexis Thambwe Mwamba expressed opposition to European Union resolution at the Human Rights Council that seeks an international, independent mission to investigate rights violations and allegations of mass graves in the wake of hundreds of killings in the Kasai provinces.

Speaking to reporters Monday on the sidelines of the council session, Mwamba said Congo's government has already agreed to allow investigators, but said they should work with Congolese authorities — not independently.

Mwamba said the four people in custody are considered "the principle actors" in the March killings of the two experts from the U.S. and Sweden and their interpreter.