The US state of Louisiana has used nitrogen gas to put a man to death for a murder committed decades ago, marking the first time the state has used the method as it resumed executions after a 15-year hiatus.

Turkey detained Istanbul mayor Ekrem Imamoglu, the main rival of President Recep Tayyip Erdogan, on charges of corruption and aiding a terrorist group in what the main opposition party on Wednesday called "a coup against our next president".

The US government on Tuesday released court documents and transcripts in a battle over information regarding Britain&s Prince Harry&s immigration to the US and his admitted drug use, but they were so heavily redacted that they revealed no significant new information.

The Antarctic researcher accused of threatening to kill colleagues trapped in a remote research station has apologised.