Local residents found the bodies in the bush in the town of Menka. Photos of a dozen dead bodies circulated on social media but could not be independently verified.
Violence between armed anglophone separatists and government forces occurs almost daily in the Northwest Region and the Southwest Region, following an escalation of the crisis in late 2016.
According to Menka residents, the Cameroonian army fended off an attack in the area in mid-May but soldiers returned overnight between Sunday and Monday. Many young people have been missing since.
"There have been some killings in Menka by the army," Nji Tumasang, deputy of the first anglophone opposition party, the Social Democratic Front, told AFP.
"We think that at first glance they are civilians because no weapon was found on them. The husband of an activist from our party is among the victims."
The Cameroonian government did not comment when approached by AFP.
Since anglophone separatists declared independence last October, dozens of officials and foreigners have been targeted for abduction.
Abductions are also used as a tool to enforce allegiance among locals who have not taken up the separatist cause.
Earlier this month, the US ambassador to Cameroon accused government forces of carrying out "targeted killings" and other abuses in the fight against independence-seeking militants.
The foreign ministry later expressed its "deep disapproval" of the comments made by US ambassador in Yaounde, Peter Barlerin.
The presence of a large English-speaking minority -- about a fifth of Cameroon's population of 22 million -- dates back to the colonial period.
It was once a German colony that after World War I was divided between Britain and France.
In 1960, the French colony gained independence, becoming Cameroon, and the following year, the British-ruled Southern Cameroons was amalgamated into it, becoming the Northwest and Southwest Regions.
For years, resentment built among anglophones, fostered by perceived marginalisation in education, the judiciary and the economy at the hands of the French majority.
Demands for greater autonomy were rejected by 85-year-old President Paul Biya, in power for more than 35 years, leading to an escalation that saw the declaration of the self-described "Republic of Ambazonia" in October last year.
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