NICOSIA (Reuters) -Greek and Turkish Cypriots on Sunday marked the 51st anniversary of Turkey's 1974 invasion of Cyprus, an event that split the island and continues to shape geopolitics in the region. Air raid sirens wailed across the southern Greek Cypriot populated parts of Cyprus at 0530 local time (0230 GMT), the hour Turkish troops landed on the northern coast in a military intervention triggered by a brief Greece-inspired coup. Turkish President Tayyip Erdogan was due to attend celebrations in north Cyprus, a breakaway state recognised only by Ankara.