The U.S. army, joined by Iraqi forces, launched the biggest air offensive since the 2003 U.S.-led invasion, the Associated Press reported.
"More than 1,500 Iraqi and Coalition troops, over 200 tactical vehicles, and more than 50 aircraft participated in the operation," the military said in a statement.
The statement added that "Operation Swarmer" was launched on Thursday morning and is "expected to continue for several days as a thorough search of the objective area is conducted."
The army says the assault is aimed at targeting Iraqi fighters near the central city of Samaarra, in the Salahuddin province.
"Initial reports from the objective area indicate that a number of enemy weapons caches have been captured, containing artillery shells, explosives, IED-(bomb) making materials, and military uniforms," said the statement.
Last month’s bomb attack on one of Iraq’s holiest Shia shrines in Samarra sparked a wave of sectarian violence across the war-torn country.
U.S. occupation forces have launched several major offensives since the invasion, including the deadly assault on Fallujah in 2004, and a series of military operations in the western Anbar province.
U.S.-Iran talks on Iraq
Iran and the United States agreed to hold bilateral talks about stabilizing Iraq, BBC reported.
It would be the first public talks between the two states since the 1979 hostage crisis, correspondents say.
Iran's Secretary of Supreme National Security Council Ali Larijani said that the Islamic Republic would agree to talks to "resolve Iraqi issues" and help stabilize the war-torn country.
Larijani didn’t say when the talks would take place or at what level.
White House spokesman Scott McClellan said the U.S. ambassador to Iraq, Zalmay Khalilzad, was authorized to talk to Iran about Iraq.
But McClellan stressed that any such talks would focus on Iraq, and not Iran’s nuclear program, which is a "separate issue" to be dealt with at the UN Security Council.
"We previously have had discussions with Iran about issue relating to Afghanistan. But this is a very narrow mandate, dealing with issues specifically relating to Iraq," he said.
The U.S. have long accused Iran of aiding the Iraqi resistance, charges strongly rejected by Tehran.