A statement from US marines based in Falluja said on Friday that two marines assigned to the 1st Marine Expeditionary Force were killed on Thursday while conducting security and stability operations in al-Anbar province in western Iraq.
It gave no further details, saying any information might be used by fighters waging daily attacks on US-led forces in Iraq.
Another US military statement issued in Baghdad said a 1st Infantry Division soldier died while "supporting Task Force Olympia operations" near Iraq's northern city of Mosul on Thursday.
The statement also gave no details but said the incident was under investigation.
The deaths raised to 1072 the number of American troops killed in action since the US-led invasion of Iraq in March 2003.