Attacks in Paris, Belgium, Netherlands: Who are the authors?

Several attacks happened in Paris, Belgium, and the Netherlands. Investigators are looking into who did them. There are questions about Iran's possible role.
French investigators think a group supporting Iran was involved in a failed attack on a US bank in Paris. The attack had similar features to other attacks in Europe. This makes people worried about Iran helping terrorists in Europe. Investigators are trying to find out how the attacks were planned. They are studying the methods used by the attackers.
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Highlights
Multiple Attacks Occurred
Several coordinated attacks happened in Paris, Belgium, and the Netherlands.
Investigators Examine Attacks
Investigators are looking into the attacks to find the people responsible.
Iran Suspected Involvement
There are questions about Iran's possible role in the attacks.
US Bank Attack Foiled
A pro-Iranian group tried to attack a US bank in Paris.
Similar Attacks Reported
The attack has similarities to other European cases.