An earthquake measuring 5.3 on the Richter Scale shook southern Philippines on Friday. There are no immediate reports of any damage or casualties.The seismology office said there was no immediate tsunami warning. Scientists have, however, cautioned that there may be aftershocks. The quake struck at 8:07 am (local time) and was centered 32 kilometers south of the city of Davao on Mindanano island at a depth of 29 kilometers.