MIAMI: Two men of Pakistani descent have been charged with plotting to provide material support to terrorists and to use a weapon of mass destruction within the US, federal prosecutors said Friday.    

The men were identified as brothers Sheheryar Alam Qazi, 30, and 20-year-old Raees Alam Qazi.

Both are naturalised US citizens originally from Pakistan and both were arrested in the Fort Lauderdale area, prosecutors said.

Few details about the plot were provided by prosecutors or outlined in a brief, three-page grand jury indictment.

Authorities said the case was not an FBI sting operation but declined any additional comment.

''Any potential threat posed by these two individuals has been disrupted,'' said Miami US Attorney Wifredo Ferrer.

In Washington, Justice Department national security spokesman Dean Boyd called the case ''an ongoing, very active investigation'' but provided no specifics.

The indictment charges that the two provided money, property, lodging, communications equipment and other support for a conspiracy to obtain a weapon of mass destruction between July 2011 and this week.

The goal was to ''use a weapon of mass destruction (explosives) against persons and property within the United States,'' prosecutors said in a news release.

It wasn't clear whether the conspirators actually did obtain explosives or what their potential targets might have been.

The Qazi brothers had initial court appearances Friday, but court-appointed attorneys for the two did not immediately respond to emails seeking comment.

An arraignment and bail hearing is scheduled for Dec 7.

They are both charged with conspiring to provide material support to terrorists, which carries a maximum 15-year prison sentence, and with conspiracy to use a weapon of mass destruction. The maximum is life in prison for that charge.

South Florida has seen several high-profile terrorism cases, including the conviction of Al Qaeda operative Jose Padilla and the convictions of five men accused of plotting to join forces with Al Qaeda to destroy a landmark Chicago skyscraper and bomb FBI offices in several cities.

More recently, a Miami Muslim cleric and one of his sons are facing trial on charges they provided thousands of dollars in financial support to the Pakistani Taliban.