Polish authorities have arrested four suspects accused of planning to send incendiary devices and explosive charges in air freight packages on behalf of a foreign intelligence services. Two other suspects are being sought internationally, a spokeswoman for the public prosecutor’s office told the Polish PAP news agency. According to the investigators, the group is said to have sent parcels with hidden explosives and other dangerous materials via courier services to other EU countries and the United Kingdom. The parcels were intended to ignite or explode during transport by land or air. Initiall…