A small explosive device went off outside offices of the Israeli airline, El Al, in the Swiss city of Zurich early on Wednesday, causing damage but no injuries. An extremist group claimed responsibility for the attack.
Police said the entrance to the offices was damaged by the explosion.
A group calling itself "For a Revolutionary Perspective" said in a faxed message to the Swiss news agency that it had carried out the bombing.
It claimed to have carried out a similar attack against the Turkish consulate, but police could not confirm a second explosion.
The organisation said its action was designed to halt "massacres" in Turkey, Kurdish areas and Palestine.
The same group, founded in 1995, is believed to have been responsible for similar, small explosions last year at the congress centre where the World Economic Forum is held in Davos, and outside two defence ministry buildings in Bern. No one was injured in those attacks.
In its communiqué, the group also called for "no more summits" like the ones held in Davos, Prague and Seattle.
Swiss federal police have described the group as left-wing extremists. Damage to the El Al office was put at SFr10,000.
swissinfo with agencies