Cameroon's defence minister called on all foreign nationals in the country's restive regions to be cautious after an American missionary died after being shot in the head amid fighting between armed separatists and soldiers in the northwest."If you must be there, immediately inform the military so we can assure your safety," Joseph Beti Assomo said on Wednesday, adding that Cameroon's English-speaking northwest and southwest regions, where separatists are fighting for an independent state, are dangerous for foreigners.Charles Trumann Wesco, a missionary from the US state of Indiana had been in the region with his wife Stephanie and eight children for nearly two weeks before Tuesday's shooting.Dave Halyman, assistant pastor at Believers Baptist Church in Warsaw, Indiana, where Stephanie Wesco's father, Don Williams, is the senior pastor, said that Williams had spoken by phone with his daughter after the shooting.Reporting Williams' account, Halyman said the shooting happened as Charles and Stephanie Wesco were in a car being driven by another missionary to the town of Bamnui from the Bamenda suburb of Bambili, where the family has been living. He said Charles Wesco was in the front seat, and two shots hit the windshield and struck him in the head. No one else was hurt, Halyman said.The family had raised financial support to work in Cameroon for two years and had visited the country two years ago on a survey trip.The United States embassy has not reacted to the shooting, but it has for some time warned US citizens against travel to the country's restive regions.Most foreign and local enterprises have left Cameroon's north and south west regions, where violence has escalated and hundreds have been killed in fighting between separatists and the military in the past year.Regional governor Deben Tchoffo said armed groups staged attacks to stop the reopening of the University of Bamenda, and the military fought back on Tuesday. He said Wesco might have been caught in crossfire.The military has killed at least four suspects in Wesco's death and arrested many others, military spokesperson Colonel Didier Badjeck told The Associated Press. He did not specify if the people detained were military personnel or separatists.The increased violence began after the government clamped down on demonstrations by English-speaking teachers and lawyers protesting what they called their marginalisation by Cameroon's French-speaking majority. Armed factions emerged after the government crackdown and have been using violence to push for an independent state they call "Ambazonia."Protests against the 85-year-old Biya's October 7 re-election have been ongoing.* Sign up to News24's top Africa news in your inbox: SUBSCRIBE TO THE HELLO AFRICA NEWSLETTERFOLLOW News24 Africa on Twitter and Facebook.