LONDON (Reuters) - Five people aboard a rescue helicopter were killed when it crashed into a utility pole in western Iran on Monday, state media reported.

The incident came amid growing concern about the safety of Iran’s aging aircraft fleet as the result of decades of U.S. trade and financial sanctions.

The helicopter went down in Chaharmahal and Bakhtiari Province on its way to pick up a pregnant woman in urgent need of medical care, state television reported.

Iran has suffered a string of plane and helicopter crashes over the past few decades. Tehran says U.S. sanctions have long prevented it from buying new aircraft or spare parts from the West to modernize its fleet.