Manila, Oct 29 (IANS): A massive earthquake measuring 6.6 on the Richter scale jolted the Philippines' Cotabato province on Tuesday, authorities said, adding that no tsunami warning had been issued.

The Philippine Institute of Volcanology and Seismology (Phivolcs) said the tremor, which struck at 9.04 a.m., hit at a depth of 7 km, about 25 km southeast of Tulunan town, Xinhua news agency reported.

The earthquake, which was tectonic in origin, can cause damage and that aftershocks are expected, it added.

The earthquake was also felt in Kaidapawan, Sarangani, Davao, Koronadal, Cagayan de Oro, General Santos, Zamboanga and Bukidnon.

Local officials in the affected provinces said the strong earthquake sent panicking people out of their houses and buildings.

The officials said that tremor cut the power supply in many of the affected provinces, knocked down electric posts and shattered glasses in some of the establishments. Patients of a local hospital were evacuated out of the building, they added.

Cotabato and its neighbouring provinces on Mindanao island are still recovering from the October 16 magnitude 6.3 earthquake that rattled the region, in which at least six people were killed and 167 injured.

The Philippines has frequent seismic activity due to its location along the Pacific "Ring of Fire", registering quakes everyday, though most are not felt.

Phivolcs records an average of 20 earthquakes a day and 100 to 150 earthquakes are felt per year.