KINSHASA – Rwandan rebels have killed at least 50 civilians in May in the volatile east of the Democratic Republic of Congo, the United Nations said on Wednesday.Twenty-two of them died in an attack Monday in the village of Kamananga in Sud-Kivu province, the United Nations humanitarian agency OCHA said, blaming the Democratic Forces for the Liberation of Rwanda (FDLR) militia group."The FDLR accuse the locals of collaborating with elements” of a local militia, a statement said."Since the start of this month, at least 50 people -- including displaced persons -- have been killed by presumed FDLR members under similar conditions,” it said.On May 5, at least 10 people – including four women working in the fields – were killed by the presumed rebels in another Sud-Kivu village.The FDLR is considered one of the main sources of instability in the east of the DR Congo, where several armed groups are still active.The rebels have been targeted by the Rwandan army in joint operations with the DR Congo army.FDLR, whose members are blamed for the 1994 Genocide against the Tutsi in Rwanda, are accused of unleashing a reign of terror on civilian populations in eastern DRC.The chief prosecutor of the International Criminal Court (ICC), Luis Moreno-Ocampo announced this week he will seek arrest warrants for the FDLR field commander, Sylvester Mudacumura, for crimes against humanity.Members of the group crossed into DRC when the genocidal machinery lost power to the RPF forces in July 1994.