OLESHKY, Russia-controlled Ukraine (Reuters) -Russian occupation authorities in the Ukrainian city of Kherson told civilians on Saturday they should leave immediately because of what they called the tense military situation as Ukraine’s forces advance. Thousands of civilians have been leaving for days across the Dnipro River after warnings about a Ukrainian offensive to recapture the city. The latest warning was delivered with renewed urgency. “Take care of the safety of your family and friends! Do not forget documents, money, valuables and clothes,” Russian-installed authorities said. At Oles…