At least 50 people were killed in weekend attacks in Congo’s conflict-battered east, authorities said Saturday. The government traded blame with Rwanda-backed rebels over who was responsible for the violence that quickly escalated the conflict in the region. The renewed violence that residents reported in and around the region’s largest city of Goma — which the M23 rebels control — was the biggest threat yet to ongoing peace efforts by both the Gulf Arab state of Qatar and African nations in the conflict that has raised fears of regional warfare.