Danish police said Friday that four city buses were destroyed in a pre-dawn fire and a fifth was vandalized with anti-Israel graffiti at a bus depot in Copenhagen.

Investigator Jens Moeller Jensen said police suspect arson and are investigating possible links to a decision last week by city transit officials to remove bus ads by a pro-Palestinian group calling for a boycott of Israeli goods.

“In paint was written ‘Boycott Israel – Free Gaza’ on at least one of the buses,” police spokesman Las Vestervig told local newspaper BT.

He said “there could be a political motive. We consider this one theory … but we cannot link it to anything for now.”

Earlier this week, local bus company Movia decided to pull ads from 35 buses in Copenhagen which called for boycotting Israeli settlement goods which read: “Our conscience is clean! We neither buy products from the Israeli settlements nor invest in the settlement industry.”

The buses were parked for the night at a depot in northern Copenhagen. Photographs from the scene showed the badly charred buses surrounded by firefighting foam.

Moeller Jensen said no one was injured and police had no suspects.

The Danish group behind the ads vowed to expand its advertising campaign urging people to boycott products from Israeli settlements after the ads were dropped from the buses.

“It’s a clear attempt to deny us our freedom of speech,” Fathi El-Abed, chairman of the Danish Palestinian Friendship Association, told AFP after bus operator Movia last week pulled the campaign.

“There is nothing whatsoever about this campaign that is harmful, discriminatory or hateful in any way,” he added.

The ads were dropped by Movia within just four days after the company “received a significant number of inquiries regarding the Danish Palestinian Friendship Association’s campaign against Israeli settlements.”

The company declined to comment when contacted by AFP but said in a statement that the campaign was “unnecessarily offensive.”

Al-Abed said his group would respond by expanding a national advertising campaign on the same subject.

“Nobody can understand why they (the bus company) decided to do this,” he said.

Feminists last year unsuccessfully petitioned Movia to drop an advertising campaign by a plastic surgery clinic that showed a naked woman’s breasts next to the tagline “New breasts,” and the city’s buses regularly feature political advertisements.

“Our support has grown because of all this attention because people are outraged, even those who’ve never had anything to do with the Palestinian cause,” Al-Abed said.