By David Gauthier-Villars, Azra Ceylan and Ece Toksabay ISTANBUL (Reuters) -Six people were killed and 81 others wounded on Sunday when an explosion rocked a busy pedestrian street in central Istanbul in what Turkish President Tayyip Erdogan called a bomb attack that “smells like terrorism”. Hundreds of people fled the historic Istiklal Avenue after the blast, as ambulances and police raced in. The area, in the Beyoglu district of Turkey’s largest city, had been crowded as usual at the weekend with shoppers, tourists and families. Video footage obtained by Reuters showed the moment the explosi…