TEHRAN, Iran – Iran closed a newspaper and detained its chief editor and cartoonist yesterday for publishing a cartoon that sparked riots by ethnic Azeris, the first such move since President Ahmadinejad came to power last year.

The heavy-handed response was a sign of the hard-line government’s concern over any internal divisions amid its confrontation with America – and suggested there were worries America may try to stir up trouble among Iran’s ethnic minorities.

The indefinite closure of the state-run Farsi language newspaper Iran came after it published a cartoon of a cockroach speaking the language of Iran’s largest ethnic minority, Azeri.

Iranian officials quickly apologized for the slur and stressed the country’s unity in the standoff with Washington, which accuses Iran of seeking to develop nuclear weapons.

“It is clear that the evil hands of foreigners are making efforts to provoke tribal, ethnic, and religious differences under the present circumstances,” State Public Prosecutor Ghorban Ali Dorri Najafabadi was quoted yesterday as saying by state press.

“Our nation is vigilant and hates the United States,” he said.

Hundreds of Azeris marched Monday in the northwestern city of Tabriz, protesting the cartoon. Some broke windows of the governor’s office, and police used tear gas to disperse the demonstrators, witnesses said. A Turkic ethnic group, Azeris make up about a quarter of Iran’s 70 million people, dominated by ethnic Persians. Azeris speak a Turkic language shared by their brethren in neighboring Azerbaijan.

They were angered by the cartoon run May 12 that suggested Azeris are stupid. It showed people from different walks of life – including an athlete and a tradesman – trying to teach the cockroach and he always answers, in Azeri, “What do you mean?”

Culture Minister Saffar Harrandi, speaking on state television Monday night, apologized for the drawing.

But an Azeri legislator, Eshrat Shayegh, said the apology came “at least one week” too late.

Tehran Prosecutor Saeed Mortazavi announced yesterday on television that the paper’s cartoonist and editor-in-chief had been detained.

“Those responsible, the cartoonist and the chief editor, were summoned and the charges were read to them.The two were taken to Evin prison,” Mr. Mortazavi said.

The daily, one of the country’s top three newspapers, was closed “due to its publication of divisive and provocative materials,” state television reported.

“We should preserve our vigilance, especially the media … and not allow, under the current very important situation the country is in now, others who pursue certain intentions to misuse the situation,” he said.