They said the massacre was carried out on Friday by militiamen from the ethnic Lendu community in the villages of Drodro and Largo, about 80 kilometers north of the regional capital of Bunia.
At least 150 people were killed in massacres in the same two villages on April 3.
Inter-ethnic massacres between the minority Hema and the majority Lendu in Ituri have claimed the lives of 50,000 people since 1999 and displaced half a million others.
The ongoing killings led to the deployment of a French-led UN peacekeeping force in the former flashpoint town of Bunia last month. But its mandate does not extend to the rest of Ituri.
At the ransacked and virtually empty hospital in Drodro, Father Desire Ngudjolo said on Saturday that Lendu militiamen had killed 23 people in a "well-coordinated" attack which began at around 5:45 am (0345 GMT) Friday. The priest said that 22 of the bodies have already been buried.
An journalist with the news agency AFP saw the body of one man, identified as that of a nurse named Nembe, as well as three wounded, one of them a woman who died of her injuries one hour later, and pools of blood.
In Largo, about two kilometers away, about one dozen bodies were strewn around the streets, some of them mutilated, said the reporter, who also saw several wounded and about 20 spent cartridge cases and several burnt-out shops.
Women cried around several graves, where residents said they had buried between 20 and 30 victims, all of them civilians.
"You don't joke around with the Lendu," someone had scrawled on the wall of a shop on the main street.
The local official in the area, Londri Ngulocha, said that a total of 408 people were killed on Friday in Drodro, Largo and in three other nearby villages.
On Sunday, 22 people were massacred at Nizi, near Bunia, according to a spokesman for the multinational peacekeeping force deployed in the region, who said the killings were probably carried out by Lendu militiamen.