By Laura Trevelyan BBC correspondent in New York

James Comey said there was no link to this week's terror alerts

Yassin Aref, the imam of the mosque, and Mohammed Hossain, the mosque's founder, were arrested overnight.

They allegedly laundered money for a man who they believed had purchased a shoulder-fired missile to assassinate the Pakistani ambassador to New York.

In fact, the man was working undercover for the US government.

The two religious leaders were detained following what US Deputy Attorney General James Comey called a sting operation.

Mr Comey said the case was not related to the Bush administration's decision earlier this week to raise the terror alert level in New York and Washington.

He stressed the two men had not been engaged in a terrorist act.

But Mr Comey claimed they were willing to assist someone who they believed to be involved in what he called "pretty bad stuff".

In a detention hearing next week the two men could face charges from money-laundering to conspiracy to conceal support for terrorism.