The United States on Tuesday announced financial sanctions against money exchanges in Iraq and Syria and an individual financier, all accused by US authorities of funneling cash to the Islamic State group.

Iraqi authorities have also moved to freeze assets tied to the individual and two companies accused of moving large volumes of cash to the militant organization and its fighters, the US Treasury Department said in a statement.

"These are the first US actions specifically targeting ISIL-affiliated money services businesses and we will continue to work aggressively to deny ISIL access to the international financial system," acting Under-Secretary Adam Szubin, the Treasury's top counter-terrorism official, said in the statement, using an acronym for IS.

The sanctioned entities include Selselat al-Thahab Money Exchange Company of Iraq, which allegedly moved IS money from last year until at least April.

The company processed money transfers for a known IS financier and conducted more than 100 transfers into IS territory, according to the Treasury.

Washington also slapped sanctions on Fawaz Muhammad Jubayr al-Rawi, an alleged senior IS financier, and Hanifa Currency Exchange, the company he owned and operated near his home in Albu Kamal, Syria.

Active as recently as May, Al-Rawi allegedly used the company solely for IS-related transactions and is suspected of facilitating payments to IS fighters as well as hosting IS leaders at his farm.

The Treasury announcement followed Defense Department reports on Tuesday that a coalition drone strike in Syria had killed three Islamic State leaders involved in plotting foreign attacks.

Treasury last month also announced sanctions, taken in concert with UAE authorities, on a Yemeni money exchange company accused of supporting Al-Qaeda in the Arabian Peninsula.