MANILA (DPA) - Hundreds of aftershocks kept residents on edge in earthquake-affected areas in the southern Philippines on Wednesday (Oct 30), as authorities rushed relief supplies and checked the safety of damaged infrastructure.

At least seven people were killed in the 6.6-magnitude tremor that jolted many parts of the southern region of Mindanao on Tuesday, the second to hit the same area in just two weeks, disaster relief agencies said.

Nearly 400 were injured in the quake, which struck just hours after most schools, offices and commercial establishments opened in the morning.

The epicentre was located near Tulunan town in Cotabato province, 972km south of Manila.

Since then, more than 270 aftershocks have been recorded by the Philippine Institute of Volcanology and Seismology (Phivolcs).

The strongest of the aftershocks was recorded at a magnitude of 6.1 and felt in "destructive" intensities, the institute added.

Many residents slept in makeshift tents outside their houses, fearing that stronger aftershocks could cause more damage to their homes.

Others were not able to sleep well overnight, according to posts on social media.

More than 8,000 people were displaced by the earthquake, the national disaster relief agency said.

Schools remained closed in more than 100 municipalities in Mindanao, while some government and commercial offices resumed operations on Wednesday.

Power was restored in most areas affected by the quake, it added.

Tuesday's earthquake jolted the same areas that were hit by a 6.3-magnitude tremor on Oct 16, which left seven people dead and 215 injured.