TEHRAN (FNA)- After three U.S. citizens were reportedly arrested on Friday for crossing illegally into Iranian territory, officials announced on Saturday that Iranian forces have monitored and registered frequent flights by two U.S. drones over Iran-Iraq bordering areas.

Eyewitnesses said that since last night the two U.S. spy planes have been flying over 'Ahmed Awa' area in the Iraqi region of Kurdistan, where the American tourists stayed before crossing into Iran.
Also they said that three U.S. military vehicles also arrived in the region on Saturday morning.
The U.S. citizens had been warned not to hike in the mountainous terrain where they were arrested, a Kurdish official told AFP on Saturday.
Beshro Ahmed, media adviser for the General Security Department in Iraq's autonomous Kurdish region, said the two men and a woman had entered Kurdistan from Turkey earlier along with a fourth American who did not join the trek because he was ill.
Ahmed named the three as Shane Bower, Sara Short and Joshua Steel, while Shaun Gabriel Maxwell stayed behind in their hotel in the autonomous Kurdish region's second largest city of Sulaimaniyah.
""On Thursday, three of them went to the summer resort at Ahmed Awa,"" Ahmed said of an area about 90 kilometers (55 miles) northeast of Sulaimaniyah.
""The (Kurdish) tourist police in the area asked them not to climb the mountains because the Iranian border was very close.
""On Friday, they went close to the mountains, and climbed them. Then they called their friend in the hotel telling him that they were arrested by Iranian forces at the border,"" Ahmed said.
Ahmed said the group had originally been in Syria before going to Turkey and eventually crossing the Turkey-Kurdistan border. They stayed in the regional capital Arbil for one night before moving on to Sulaimaniyah.
The reason for the presence of these American nationals is not known. The western media, in the past few days, extensively propagated that these three U.S. personnel have been kidnapped.