Iran on Tuesday warned Bulgaria against allowing its territory to be used for US military operations, saying any assistance that facilitated American attacks on the Islamic Republic would amount to complicity in "aggression and war crimes", Reuters reported.The warning came after Bulgaria said it would seek parliamentary approval to station up to eight US aerial refuelling tanker aircraft at the Bezmer military base, around 260 km southeast of Sofia.Iranian Foreign Ministry spokesperson Esmail Baghaei said any activity that enabled US military strikes on Iran would make Bulgaria "an accomplice of aggressors and lawbreakers", according to Iranian state media cited by Reuters.The proposed deployment involves tanker aircraft primarily used to provide mid-air refuelling to other military aircraft.The development comes as the United States and Iran continue to exchange strikes after an interim ceasefire agreement reached last month collapsed, fuelling concerns of a return to a broader conflict in the region.