Three doctors from South Korea have been killed in north-east Nigeria.
The doctors were attacked in the town of Potiskum where they were working at the general hospital.
Two had their throats slit and the other was beheaded at their quarters late on Saturday or before dawn on Sunday.
The attack happened in an area where the Boko Haram group is active. More than 600 people are believed to have been killed in 2012 by the group, which wants to overthrow the government and create an Islamic state.
On Friday, nine polio vaccination team members - all said to have been women - were shot dead in northern Nigeria. Some were killed in Kano and the others at a health centre in Hotoro, outside the city.
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