An medium-strength earthquake rocked north- western Turkey late Friday, registering 5.2 on the Richter scale, but there were no immediate reports of casualties, local media reported, according to dpa. The epicentre lay south of the Marmara Sea in Balikesir Province, where the minaret of one village was toppled and two homes collapsed, the Anadolu news agency reported. Tremors were felt in Istanbul. Seven years ago, more than 18,000 people were killed when the region was hit by an earthquake measuring 7.4 on the Richter scale. There have since been constant fears of further devastating quakes.