The death toll from a powerful quake that struck the central Philippines rose to 43 as landslides struck a mountainous area, a regional military official said.

At least 29 were killed by landslides while 10 others were crushed by collapsing buildings in the mountainous town of of Guihulngan on Negros island, said Colonel Francisco Patrimonio.

Four other people were killed in other parts of Negros which also suffered widespread power outages and damaged roads and bridges, hampering rescue efforts, the colonel told reporters.

"Looting is now rampant in Guihulngan which forced us to commit (more troops) with the Philippine national police," he added.

The 6.8-magnitude earthquake struck off the coast of the central Philippines in a narrow strait between the heavily populated island provinces of Negros and Cebu.

Almost four hours after the quake struck, a 6.2-magnitude aftershock hit the central Philippines again, panicking rescuers once more.