Nigeria's Defence Minister Bashir Magashi has said the country has increased security on its border with Chad after the country's president was killed.

The minister said Nigeria was battling insurgency within its borders and was mindful of external threats that would come from the influx of refugees.

Only Nigerians living in Chad will be allowed in the country, Reuters news agency reports.

Nigeria borders Chad in the north-east where Boko Haram militants have carried out attacks recently.

Chad is seen as an important country to the international efforts to combat insecurity in West Africa.