At least 26 people were killed earlier this week in the eastern Democratic Republic of the Congo in an attack blamed fighters from the Allied Democratic Forces (ADF), a monitoring group and sources said on Thursday. On Wednesday local government and humanitarian workers said 13 bodies had been found after the attack in Rwenzori area of Beni region and several people were missing. The Kivu Security Tracker, a local monitoring organisation that has experts in the region, said the toll had risen to 26 after more bodies were found in the neighbouring villages. "Thirteen other corpses were picked up after searches in the forest," a humanitarian source told AFP, saying the death toll could still grow. The ADF is the deadliest of scores of armed militias that operate in the mineral-rich east of the Democratic Republic of Congo. Many are a legacy of two regional wars from 1996 to 2003. More than 500 civilians have been killed in the provinces of North and South Kivu alone since the start of the year, according to an AFP toll based on NGO figures and local sources. The ADF is a historically Ugandan Islamist group that has holed up in eastern DRC since 1995. The United States has said the ADF is linked to the Islamic State (IS), and was known as ISIS-DRC or Madina at Tauheed Wau Mujahedeen. DR Congo President Felix Tshisekedi this month proclaimed a 30-day "state of siege" -- effectively martial law -- in North Kivu and neighbouring Ituri province in a bid to curb bloodshed by the ADF. str-bmb/pma/pvh