Turkish forces crossed into Iraq Thursday to strike at Kurdish rebels and warplanes pounded their bases in retaliation for the death of 24 soldiers, officials said. "A large-scale land operation, backed by air strikes, has begun in five separate spots inside Turkey and across the border with 22 battalions," the Turkish military said in a statement posted on its website. The 22 battalions comprise commando units as well as gendarmerie and special forces, it added, without specifying how many had entered Iraq. Analysts said the total troops deployed would be 10-15,000. "The air and land operation is under way," Prime Minister Recep Tayyip Erdogan told reporters right after the military annoucement. "The operation is result-oriented," he said, without elaborating. In response to the Turkish move, the separatist Kurdistan Workers' Party (PKK) said it would "welcome" the ground forces. "If they want to come, let them come," Dozdar Hammo, a PKK spokesman, told AFP. "We will welcome them here." Hammo said no Turkish troops had yet crossed the border into northern Iraq, but said Ankara's jets were overhead.