ISTANBUL (Reuters) - An unidentified assailant set fire on Monday to an Istanbul arts center, CCTV footage showed, and its founder, a prominent critic of the Turkish government, said he suspected a political motive for the attack.

The Istanbul prosecutor’s office said it was investigating the incident.

The CCTV footage showed what appeared to be a man shortly after midnight dousing the doorstep of the building with liquid from a cannister. This was followed by a bright flash and fire.

“Our guard heard an explosion ... and ran outside,” Mujdat Gezen, founder of the Mujdat Gezen Arts Centre, told Reuters. “There is some damage to the front of the building, but nothing serious, we can fix it.”

Gezen, an actor and staunch secularist who has often criticized the ruling AK Party, which has Islamist roots, said he believed the fire was an attack on those opposed to an April 16 referendum that would boost the Turkish president’s powers.

President Tayyip Erdogan has said those who vote “no” in the referendum are siding with supporters of terrorism and a failed military coup. Critics say the proposed constitutional changes would lead to one-man rule and undermine basic freedoms.

Gezen said his center had also received threats in the past.

Turkey has become more deeply polarized since the July 15 failed coup, with authorities arresting tens of thousands of people suspected of backing the putsch, including judges, journalists and soldiers, in a crackdown that has alarmed Ankara’s NATO allies and human rights groups.