Israeli Prime Minister Benjamin Netanyahu is promising a strong reaction after an attack on Israeli tourists that he says was carried out by Iran. 

A bus carrying mostly Israeli youth in a Bulgaria exploded near an airport Wednesday, killing at least six people and wounding at least 32 others, the Bulgarian Foreign Ministry said. Witnesses told Israeli media that the huge blast occurred soon after someone boarded the vehicle.

A Bulgarian news agency is also reporting that two pregnant women and an 11-year-old Israeli girl are among the wounded. 

Bulgarian media is reporting that one of the victims killed is a local tour guide. Nine of the tourists are reportedly still missing, according to Haaretz news. 

The incident took place in the Black Sea resort city of Burgas, some 250 miles east of the capital, Sofia. Images shown on Israeli media showed smoke billowing from the scene -- a parking lot at the area's airport where tourists had apparently just landed.