Heavy Shelling in Kharkiv on 6th Day of Russian Invasion of UkraineUkraine's second-largest city faced increased Russian shelling Tuesday, while a column of Russian forces stretched out along a road north of the Ukrainian capital, Kyiv, on the sixth day of Russia's invasion of its neighbor. The Ukrainian Foreign Ministry shared a video of one strike at the Kharkiv Regional State Administration building in the center of the city that left a huge ball of fire and smoke as several cars were passing through. "The strike against Kharkiv is a war crime," Ukrainian President Volodymyr Zelenskyy said in a video statement. "This is state terrorism on the part of Russia." An emergency services official said the strike killed at least six people and injured 20 others. EU foreign policy chief Josep Borrell said Tuesday that Russian shelling of civilian infrastructure that took place Monday in Kharkiv "violates the laws of war." Kremlin spokesman Dmitry Peskov dismissed allegations of war crimes and told reporters that "Russian troops don't conduct any strikes against civilian infrastructure and residential areas." Ukraine also reported Tuesday that troops from Russian ally Belarus had entered Ukraine's Chernihiv region. In Poland, NATO Secretary General Jens Stoltenberg said NATO will hold both Russia and Belarus accountable for what is happening in Ukraine. "President Putin has shattered peace in Europe. Allies condemn the unjust and brutal invasion of Ukraine. The Russian assault is totally unacceptable and it is enabled by Belarus." Stoltenberg reiterated that NATO will not be sending troops to fight in Ukraine, nor will it be patrolling Ukrainian airspace, while calling on Russia to immediately "stop the war" and withdraw its forces. Speaking alongside Polish President Andrzej Duda, Stoltenberg thanked Poland for opening its borders to refugees fleeing the fighting in Ukraine. The U.N. refugee agency said Tuesday that more than 660,000 people, most of them women and children, had fled Ukraine to neighboring countries since Thursday. The U.N. human rights office reported at least 136 civilian deaths in Ukraine. "The real toll is likely to be much higher," spokesperson Liz Throssell said during a briefing. Russian forces north of Kyiv are being closely watched amid fears of an assault on the capital. U.S. defense officials and British intelligence said the convoy has not made much progress toward the city in recent days, with one U.S. official telling reporters Monday the "main push" was 25 kilometers outside the city. Satellite images from Maxar Technologies have shown the convoy getting longer, stretching for about 64 kilometers in images taken Monday. "For the enemy, Kyiv is the key target," Zelenskyy said in a video message late on Monday. "We did not let them break the defense of the capital, and they send saboteurs to us ... We will neutralize them all." The Kremlin said Russian President Vladimir Putin told French leader Emmanuel Macron in a call Monday that a settlement can only happen if Russia's "legitimate security interests" are considered, including the demilitarization of Ukraine. Australia announced plans Tuesday to send missiles to Ukraine as part of a $50 million package. Australian Prime Minister Scott Morrison told reporters the lethal and non-lethal aid comes in response to a call by Zelenskyy for Ukrainian allies to send his country military support to oppose the Russian invasion, and "that's exactly what we're doing," Morrison said. U.S. lawmakers are considering a White House request for $6.4 billion in military and humanitarian aid for Ukraine. Ukrainian Ambassador to the U.S. Oksana Markarova told a group of U.S. senators in a meeting Monday that Ukraine needs more weapons. "It's David versus Goliath," said Senator Jim Risch, the top Republican on the Foreign Relations Committee, noting the much larger size of Russia's military. "I think that any human being reading the reports coming out of there realize that this is dire." Markarova also advocated for U.S. sanctions against Russia's oil and gas sectors after joining with numerous other countries to apply economic pressure on Putin with sanctions targeting top officials, business figures and the Russian financial system. "We need to consider stopping the flow of energy from Russia to the United States and enlist our allies in the same cause," Democratic Senator Richard Blumenthal said. A round of peace talks between Ukrainian and Russian officials ended after five hours Monday with no resolution, as the Ukrainian side demanded an immediate cease-fire and withdrawal of Russian troops. The two sides are expected to meet again, but no date has been set. U.S. officials expressed skepticism over Russia's intentions during the talks. "Diplomacy at the barrel of a gun, diplomacy at the turret of a tank — that is not real diplomacy," State Department spokesperson Ned Price told reporters Monday. "We are ready and willing, just as our Ukrainian partners are, just as our European allies are, to engage in real, in substantive, in genuine diplomacy in order to see if we can find a way out of what is a needless, brutal conflict." Russian negotiator Vladimir Medinsky said Monday that Russia's goal was to come to an agreement that was in the interest of both sides. Zelenskyy on Monday repeated his call for a no-fly zone to prevent Russian attacks from the air. "Fair negotiations can occur when one side does not hit the other side with rocket artillery at the very moment of negotiations," Zelenskyy said. In response to a question from Voice of America, the Pentagon said the United States was not considering such a measure. "Airspace over Ukraine remains contested. Russians have not achieved air superiority over the whole country. Ukrainian air defenses remain intact and viable, both in terms of aircraft and missile defense systems," a senior U.S. defense official told reporters Monday. The official added that it appeared Russian forces were trying to section off the eastern part of Ukraine by controlling land from Kharkiv to Mariupol in the south. Neither city had been broken by Russian advances, although Kharkiv has seen the "heaviest fighting," according to officials. Russian President Vladimir Putin has now committed to the invasion nearly 75% of the combat power Russia pre-positioned around Ukraine's borders. But videos posted on social media show that lines of Russian tanks and armored vehicles have been wiped out. Warplanes and helicopters have been shot down, according to officials, and Russian troops have been stranded on roadsides after their vehicles ran out of fuel. Some information for this report came from The Associated Press, Agence France-Presse and Reuters.