Kiev, March 3 : In his latest video message, Ukrainian President Volodymyr Zelensky has urged the citizens of his country to keep up the fight against Russia as Moscow's invasion of Kiev has entered its seventh day. In the video posted on Facebook late Wednesday night, the President says: "Every occupier should know: they will receive a fierce rebuff from the Ukrainians. "We are a nation that broke the enemy's plans in a week... But we stopped them." Addressing the citizens from an undisclosed location, Zelensky said the Russian servicemen who have been captured in Ukraine "do not know why they are here", and that the "enemy soldiers are fleeing back to Russia", the BBC reported. He called the troops "confused children" being "used" by their leaders in Russia. The President thanked the citizens in the cities of Konotop, Bashtanka, Energodar and Melitopol, who he claimed had blocked roads to prevent the Russian troops from entering. Just hours after Zelensky video address, Kiev was reportedly hit by at least four explosions on Thursday morning, the BBC said. Of the four blasts, two reported reportedly went off in the city centre, and the two others near a metro station. Air raid sirens were heard in the capital city following the explosions. Also on Thursday morning, Mayor Igor Kolykhaev of Kherson, a key port city in southern Ukraine,claimed that Russian troops have seized control, making it the first major city to be taken by Moscow since it began its invasion on February 24. In a Facebook post, Kolykhaev said that Russian forces were now in control of Kherson and that the troops had forced their way into the city council building and imposed a curfew on residents, the BBC reported. He further said that there were no Ukrainian forces in the city, which is located on the banks of the Dnieper River and has a population of over 280,000 people. Meanwhile in Kharkiv, Ukraine's second largest city, Russian shells continued to fall, reportedly killing and wounding dozens of civilians, while troops have also surrounded Mariupol, another strategic port city. Since the assault began a week ago, Ukraine has claimed that more than 2,000 civilians have died, while the UN Refugee Agency (UNHCR) has said that the conflict has also led to some 1 million people to flee the country. The UNHCR has predicted the conflict will leave some 12 million people internally displaced and in need of relief. Meanwhile, Russia has for the first time admitted that 498 of its troops were killed, with 1,597 injured. /IANS