The cartoonist and the editor-in-chief of the “Iran” newspaper were arrested over the lampoon that was deemed to insult Iran’s Azeri minority, Teheran’s chief Prosecutor Saeed Mortazavi said.

“Some charges were brought against both of them and they were transferred to Evin prison,” he told state television. He did not specify the charges.

He added the publishing manager of the newspaper, Gholamhossein Eslamifard, had been summoned to court.

The official IRNA news agency said the cartoonist, Mana Neyestani, and the editor-in-chief, Mehrdad Qasemfar, were detained for “further investigation”.

Furious members of the Azeri minority pelted government buildings and banks with stones in Tabriz on Monday night, enraged by the cartoon, eyewitnesses in the city told Reuters.

The Press Supervisory Board closed the paper for stirring up ethnic rifts, state television reported.

The cartoon, which appeared in Friday’s edition of Iran, showed a boy repeating the Persian word for cockroach in different ways while the uncomprehending bug in front of him says “What?” in Azeri.

Neyestani’s relatives told Reuters he had not intended to insult Azeris.

The Azeris of northwestern Iran speak a language related to Turkish. Although Azeris have many luminaries among Iran’s commercial elite, Iran’s majority Persians mock them in jokes.

The conservative Siyasat-e Rouz daily on Sunday said a crowd of Azeris had set fire to Iran’s local office in the city of Orumiyeh, where Azeris make up the majority of the population.

Azeris account for about 25 percent of the overall population of the Islamic Republic.

People in Tabriz said it was quiet on Tuesday but that there was a heavy police presence on the streets.