Germany’s foreign minister cautioned Israel Thursday against assigning blame for the terror attack on a bus of Israeli tourists in the Bulgarian resort town of Burgas a day earlier.

Guido Westerwelle also condemned the suicide attack, which left five Israelis and a Bulgarian dead and dozens injured.

“There is no data about the perpetrators and Israel should be careful in commenting on the attack,” Wetserwelle told the German newspaper Deutsche Welle.

Israeli officials have pointed to Iran or its proxy Hezbollah as the likely culprits behind the suicide bombing.

Several attempted attacks on Israeli and Jewish targets in Asia and Europe over the last six months have been linked to Iran.

On Wednesday night, Prime Minister Benjamin Netanyahu said that “all the signs point to Iran… the murderous terror of the Iranians continues to hurt innocent people. This is a terrorist Iranian aggression revealing itself all over the world. Israel will respond forcefully to the Iranian terror.”

Defense Minister Ehud Barak and Deputy Foreign Minister Danny Ayalon also blamed Iran for the attack, but Meir Javedanfar, an Iran expert at the Interdisciplinary Center in Herzliya, was far more cautious. Javedanfar acknowledged that there were reasons to suspect Iran, including the fact that the tragedy in Burgas took place 18 years to the day after a bombing attack on the Jewish community center in Buenos Aires, Argentina, which claimed the lives of 85 people. Investigations into the Buenos Aires attack concluded that Iran was responsible. Nevertheless, Javedanfar said that it was “far too early to conclude who was behind the bombing in Bulgaria” and that Israel must “wait for the results of a full investigation before a credible conclusion can be made.”