At least six people killed in explosion in Istanbul

At least six people have been killed and 53 others wounded in an explosion in a busy area in the heart of Istanbul.

The blast ocurred on the pedestrian İstiklal Avenue, which is popular among local and foreign tourists lined with shops and restaurants, at around 4:20 pm local time.

“Initial assessments showed that four were killed and 38 others were injured in the blast,” said Governor Ali Yerlikaya. The chief prosecutor’s office in Istanbul has appointed five prosecutors to investigate the deadly blast.

The Turkish Radio and Television Supreme Council (RTÜK) has imposed a broadcast ban on the explosion.

There was no immediate explanation or claim of responsibility for the blast but Turkish President Erdogan declared that the explosion was a "bomb attack." 

It is unclear what caused the explosion, which appears to have been captured on numerous videos circulating on social media.

Emergency services are at the scene with  heavy police presence around Istiklal Street, which had been cordoned off. Helicopters were circling overhead as ambulances went back and forth.

The street - usually packed with shoppers - was previously targeted by a suicide bomber in 2016.

Istanbul has been the scene of attacks before. On New Year's Day in 2017, a gunman shot and killed 39 people at a nightclub. Almost 80 others were also injured. In 2003, a series of suicide bombings was carried out using trucks at four locations in the city.