YAOUNDE: Nigeria's president is promising deeper collaboration with its neighbors in the fight against Islamic extremism after a two-day visit to Cameroon.

Nigeria's President Muhammadu Buhari headed home Thursday after meeting with his counterpart for two days of talks focused around the threat posed by Boko Haram.

Cameroon along with neighbors Niger and Chad are helping Nigeria's military in the fight against the group. Some 20,000 have died in the six-year-old uprising.

But some observers say the multinational effort has been hampered by Nigeria's concern about foreign troops on its soil.

Before leaving Cameroon, Nigeria's president said "none of us can succeed alone."

Nearly 2 million people have been displaced by Boko Haram-related violence.