Iran's Foreign Minister Mohammad Javad Zarif has held a phone conversation with his Ukrainian counterpart Vadym Prystaiko on the regrettable crash of a Ukrainian passenger plane in Tehran, which killed many Iranian and foreign nationals, including those of Ukraine.In the Wednesday phone conversation, the two ministers expressed deep regret over the heart-breaking accident, and exchanged condolences over the deaths of Iranian and Ukrainian nationals.The reasons for the crash are still under investigation.