The Ukrainian army said Friday it only hit "military targets", a day after Russia accused Kyiv of firing drones at a hotel and cafe in Ukraine's occupied south, killing 27 people.

Russian-installed authorities in Ukraine's southern Kherson region said those killed were revellers celebrating the New Year and that two of the dead were children, describing the incident as a "terrorist act".

Airstrikes killed seven people in Yemen on Friday as a Saudi-led coalition attacked UAE-backed separatists who have seized huge swathes of territory, an official for the group.

More than 20 people were also wounded as seven airstrikes hit a camp in Al-Khasah, said Mohammed Abdulmalik, head of the separatist Southern Transitional Council in Wadi Hadramaut and Hadramaut Desert.

A top Iranian security official on Friday warned U.S. President Donald Trump against intervening in protests gripping the country, saying it would "destabilize the entire region".

"Trump should know that any American interference in this internal matter would amount to destabilizing the entire region and harming American interests," Ali Larijani, who heads Iran's highest security body said.

President Donald Trump said Friday that the United States is "locked and loaded" to respond if Iran kills protesters, after cost-of-living demonstrations in the country turned deadly.

Protesters and security forces clashed in several Iranian cities Thursday with six reported killed in the first deaths since the unrest escalated.

Yemen's Hadramawt province has launched an operation to "peacefully" take back military sites after a sweeping advance by UAE-backed separatists, its governor said on Friday.

"This operation is not a declaration of war, nor an attempt to escalate tensions," Salem Al-Khanbashi said in a statement reported by the official Saba Net news agency, shortly after he was also appointed to lead the Saudi-backed National Shield forces in Hadramawt.

Ukrainian President Volodymyr Zelensky on Thursday said Russia was carrying the near four-year war "into the New Year" with more than 200 drones fired at Ukraine, mainly targeting energy infrastructure.

Separatists from Yemen's Southern Transitional Council said on Thursday that Saudi-aligned government forces would enter territories seized by the UAE-backed group, in a step that appeared unlikely to satisfy Riyadh after it repeatedly demanded their full withdrawal.

Several dozen people are presumed dead and around 100 injured after a fire ripped through a crowded bar in the luxury Swiss ski resort town of Crans-Montana, police said early Thursday.

Iran's prosecutor general said on Wednesday that economic protests that had gripped the country were legitimate, but any attempt to create insecurity would be met with a "decisive response".

Russia's defense ministry published a video Wednesday of a downed drone that it says Ukraine launched at President Vladimir Putin's residence in north-west Russia this week -- a claim Kyiv has denied as a "lie."