A prominent journalist and television presenter from Cameroon's restive anglophone region, where a violent separatist campaign has sparked a massive government crackdown, has been jailed for "attacking state security", her lawyer told AFP on Thursday.Mimi Mefo, who heads English news for privately-owned Equinoxe broadcasting, was charged by a military tribunal late on Wednesday and placed in preventive detention in the New-Bell prison in Cameroon's commercial capital Douala, lawyer Alice Nkom said.She will be tried by a military court on Monday, Nkom said. Mefo was charged over a social media post which said "the army was responsible for the death of US missionary Charles Trumann Wesco who died in October after an attack in the English-speaking North West region," her lawyer said.Nkom said her client had also posted the Cameroonian government's version of what happened - that Wesco had died after a raid by anglophone separatists."Her innocence is established and the proof that her imprisonment was planned is overwhelming," said the National Union of Cameroon Journalists.Media watchdog Journalists Without Borders also called for her immediate release, saying: "Journalists who cover the anglophone crisis are not criminals!"Wesco had just arrived in northwestern Cameroon and was still in the process of settling in when he was shot in the head while driving to do some shopping in Bamenda, one of the main cities in the region.Eighty percent of Cameroon's population are French speakers while the rest are anglophones, who are concentrated in the country's troubled west.In 2016, resentment at perceived discrimination in education, the judiciary and the economy fanned demands for autonomy in the North West and neighbouring South West regions. Radicals declared an independent state called the "Republic of Ambazonia" and took up arms soon after.Separatists have since attacked troops and police, boycotted and torched schools and attacked other state symbols, prompting a brutal official crackdown.At least 400 civilians and 175 police and soldiers have been killed this year, according to an NGO toll. More than 300 000 other have fled the violence, some crossing into neighbouring Nigeria. * Sign up to News24's top Africa news in your inbox: SUBSCRIBE TO THE HELLO AFRICA NEWSLETTERFOLLOW News24 Africa on Twitter and Facebook.