Authorities are investigating reports of an assault on a Muslim cleric and vandalism and harassment of worshippers at a Detroit-area mosque.

The FBI is involved in the case, and Gov. Jennifer Granholm has offered state aid if needed, according to The Detroit News.

The reports involve Al-Islah Islamic Center in Hamtramck, a city of about 23,000 surrounded by Detroit.

On Sunday, youths entered the mosque, took shoes that worshippers had left by the door and threw them at congregants, mosque officials say. They say twice this year, objects were thrown through mosque windows.

On Feb. 9, three men accosted Imam Muhammad Uddin, and he was hit with a shovel, said Al-Islah President Abdul Motlib. He said Uddin did not require treatment for a leg injury but was unable to attend the mosque for two days.

"There is more that can be done about this situation than what the city has done," Motlib said. "I understand we don't have enough police. If they want to bring in the Wayne County (sheriff) or the state police, it is easy to control this."

In addition, 15 Muslim merchants have been mugged within two weeks, according to a news release from the Council on American-Islamic Relations.

"We are disturbed by the vandalism of the mosque and the high frequency of attacks that have taken place in a very short time span," said Dawud Walid, the group's Michigan executive director.

On Monday, council representatives met with Granholm and state Civil Rights Director Linda Parker and requested better policing near the mosque.

City Manager Donald Crawford said Hamtramck has many Arab-American businessmen and it is understandable that they would be targets of crime. He said he was unaware of any assault on the imam.

In 2004, a dispute over the mosque's use of loudspeakers for the five daily calls to worship led to a ballot issue. Opponents of the call sought to repeal part of the municipal noise ordinance, but voters rejected the proposal.