* Attack blamed on Ugandan rebels ADF-NALU
* UN helicopters intervened to help Congo army retake village
* ADF-NALU has stepped up attacks this year in Congo
By Pete Jones
KINSHASA, Dec 26 (Reuters) - At least 40 civilians have been killed in a rebel attack on a village in eastern Democratic Republic of Congo, local officials and civil society groups said.
Thomas D'Acquin, head ...