Regarding the assassination of Russian Ambassador in Turkey:
In Islam, ambassadors are not killed. Diplomatic Immunity is given even to false prophets at war with Islam.
Nu’aim reported: I heard the Messenger of Allah, peace and blessings be upon him, speaking to those who were reading the letter of Musaylimah the Liar, “What do you both say?” They said, “We say what he said.” The Prophet said, “I swear by Allah, were it not that messengers are not killed, I would strike both of your necks.”
Sunan Abu Dawud 2761Grade: Hasan (fair) according to Ibn Hajar
Ibn Qudamah said, “People who come from states which are at war with us who are given a covenant of peace cannot be killed, nor can their lives or property be transgressed against.”
There has been a famous case in our history where a muslim ruler went against these teachings of the Prophet Muhammad and suffered a terrible consequence. Muhammad II, the Shah of the Khwarezmian Empire killed Genghis Khan’s ambassadors and his kingdom was annihilated.
“Genghis sent an envoy of three men to the Shah, to give him a chance to disclaim all knowledge of the governor’s actions and hand him over to the Mongols for punishment. The shah executed the envoy (again, some sources claim one man was executed, some claim all three were), and then immediately had the Mongol merchant party (Muslim and Mongol alike) put to death. These events led Genghis to retaliate with a force of 100,000 to 150,000 men that crossed the Jaxartes in 1219 and sacked the cities of Samarkand, Bukhara, Otrar and others. Muhammad II’s capital city, Urgench, followed soon after.
Genghis Khan’s revenge was considered brutal, even by Mongol standards. His campaign resulted in the complete annihilation of Khwarezm cities, destruction of countless historical artifacts and records, and arguably the bloodiest massacre the world saw until the 20th century.”