UPDATE 2-Turkey's opposition strikes blow to Erdogan with Istanbul mayoral win

Turkey's opposition has dealt President Tayyip Erdogan a stinging blow by winning control of Istanbul in a re-run mayoral election, breaking his aura of invincibility and delivering a message from voters unhappy over his ever tighter grip on power. Ekrem Imamoglu of the secularist Republican People's Party (CHP) secured 54.21% of votes, the head of the High Election Board announced on Monday - a far wider victory margin than his narrow win three months ago.