An explosion on a bus carrying Israeli tourists in Bulgaria has killed at least six people and wounded about 30 others.

Wednesday's blast occurred in the Black Sea city of Burgas, about 400 kilometers from the capital, Sofia. Police say several other buses at the site were also damaged.

Israeli officials have blamed Iran for the explosion. Foreign Minister Avigdor Lieberman said Bulgarian authorities informed the Ministry that the explosion was caused by a bomb placed on the bus.

No group has claimed responsibility. But Israeli Prime Minister Benjamin Netanyahu said that similar attacks on Israeli tourists in India, Thailand and other places point to Iran. He did not clarify.

U.S. President Barack Obama condemned the bombing as “a barbaric terrorist attack.”