At least 16 people were killed in an attack in the Democratic Republic of Congo's conflict-plagued east, believed to be the work of armed Islamists, military and local sources said Tuesday.

According to local civilian sources the victims of Monday's attack, including two women, had been taken hostage weeks earlier by members of the Allied Democratic Forces (ADF), which the US says is linked to the Islamic State group.

The hostages were knifed to death along a main highway near Idohu, in the restive Ituri province, local official Dieudonne Malangai said.

Ituri's military governor Johnny Luboya Nkashama speaking in Komanda, some 40 kilometres (25 miles) from the incident, condemned the  killings.

"We will reinforce our presence in the region," he told AFP.

The vast central African country's government has placed Ituri and the neighbouring North Kivu province under a state of siege since May, in a move aimed at stepping up the fight against armed groups.

The ADF is the deadliest of the militias operating in the region. 

It began as an armed Ugandan Muslim group, and has been active in mineral-rich eastern Democratic Republic of Congo for 30 years. 

The DRC's Catholic Church says the ADF has killed around 6,000 civilians since 2013, while a respected US-based monitor, the Kivu Security Tracker (KST), blames it for more than 1,200 deaths in the Beni area alone since 2017.