Niger's defence ministry says 29 soldiers have been killed in an assault by suspected jihadists in the west of the country.

It's the deadliest such attack since the army seized power in a coup at the end of July.

In a televised statement officials said the troops had been targeted by more than a 100 militants, using weapons including improvised explosive devices.

Three days of national mourning have been declared.

Jihadist attacks on the army have risen since the military seized power and stated that it had staged the coup to be better able to fight militants.