The International Committee of the Red Cross (ICRC) is ready to direct operations to evacuate civilians trapped in the besieged city of Mariupol in southern Ukraine from Friday, provided it has security guarantees, the organisation said in a statement. Ewan Watson, ICRC spokesperson, said Ukraine and Russia must agree on the exact terms of the operation, which is planned for Friday, adding that "tens of thousands" of lives depend on its success. "For logistics and security reasons, we’ll be ready to lead the safe passage operation tomorrow, Friday, provided all the parties agree to the exact terms, including the route, the start time, and the duration," Watson told Reuters in Geneva. A convoy of Ukrainian buses set out for the southern port city of Mariupol on Thursday to try to reach trapped civilians, Deputy Prime Minister Iryna Vereshchuk said. She said the International Committee of the Red Cross had confirmed that Russia had agreed to open a humanitarian corridor to the besieged city where tens of thousands of civilians remain after weeks of Russian bombardment. The mayor of the besieged city said this week that up to 170,000 residents were still trapped with no power and dwindling supplies. For their part, the Russian Defence Ministry announced on Wednesday the opening of corridors for the evacuation of civilians who have been trapped for weeks in the Greek-founded city. The Red Cross has always insisted on the need to pay attention and negotiate even the smallest detail with all parties, even with the military leadership in the regions. The Ukrainian government is planning to send 45 buses to evacuate civilians from the port city. This decision was made following Russia's announcement that it was "ready to allow access to humanitarian convoys from Mariupol" to the city of Zaporizhia, according to Ukrainian Deputy Prime Minister Iryna Vereshchuk. Elsewhere, Turkey is working to bring together the Ukrainian and Russian foreign ministers for talks after hosting peace negotiations in Istanbul this week, Foreign Minister Mevlut Cavusoglu said on Thursday, adding the meeting could happen within two weeks. Negotiators from Ukraine and Russia held the first face-to-face talks in more than two weeks in Istanbul this week, during which Ukraine presented written proposals to stop the Russian invasion. Speaking to broadcaster A Haber, Cavusoglu said Turkey had not seen the full implementation of the decisions from the talks in Istanbul, including the withdrawal of Russian forces from some areas, but added significant progress was still made. Cavusoglu said on Thursday that Russian oligarch Roman Abramovich, who is sanctioned by European nations over Russia's invasion of Ukraine, was "sincerely" working to end the war. He has been liaising between Kyiv and Moscow since the invasion began on Feb. 24, Cavusoglu said. Abramovich made a surprise appearance at Ukraine-Russia negotiations in Istanbul on Tuesday. The UN nuclear watchdog will establish online monitoring missions to the Russian-occupied Chernobyl and Zaporizhzhia nuclear plants in Ukraine, the head of Ukraine's state nuclear company said on Thursday. Energoatom CEO Petro Kotin said the International Atomic Energy Agency (IAEA) should use its influence to ensure Russian nuclear officials do not interfere in the operation of nuclear plants occupied by Russian forces that invaded Ukraine last month. "(The IAEA) can influence this and they must influence this, and this question will be discussed," Kotin said. More than 2.3 million Ukrainians have so far crossed into Poland but as many as 380,000 people have returned to Ukraine. Some are struggling to find lodging and work in Poland while others have elderly relatives they left behind when they fled. FRANCE 24’s Ellen Gainsford reports from the border crossing at Medyka, Poland. READ MORE: Why do so many cities in Ukraine and Crimea have Greek sounding names?