Russia has begun a large-scale military attack on Ukraine, its southern neighbour, on the orders of Russian President Vladimir Putin.   There are reports of attacks on Ukrainian military infrastructure across the country, and Russian convoys entering from all directions. Here is what we know so far. Putin orders attack In a televised speech at 05:55 Moscow time (02:55 GMT), Mr Putin announced a "military operation" in Ukraine's eastern Donbas region. This area is home to many Russian-speaking Ukrainians. Parts of it has been occupied and run by Russian-backed rebels since 2014. Mr Putin said Russia was intervening as an act of self-defence. Russia did not want to occupy Ukraine, he said, but would demilitarise and "de-Nazify" the country. He urged Ukrainian soldiers in the combat zone to lay down their weapons and go home, but said clashes were inevitable and "only a question of time". And he added that any intervention from outside powers to resist the Russian attack would be met with an "instant" response. Explosions heard across the country BBC correspondents heard loud bangs in the capital Kyiv, as well as Kramatorsk in the Donetsk region of eastern Ukraine. Blasts have also been heard in the southern port city of Odesa. Ukraine's President Volodymyr Zelensky said Russia had carried out missile strikes on Ukraine's infrastructure and on border guards. Russia's defence ministry has denied attacking Ukrainian cities - saying it was targeting military infrastructure, air defence and air forces with "high-precision weapons". Tanks and troops enter UkraineTanks and troops have poured into Ukraine at points along its eastern, southern and northern borders, Ukraine says. Russian military convoys have crossed from Belarus into Ukraine's northern Chernihiv region, and from Russia into the Sumy region, which is also in the north, Ukraine's border guard service (DPSU) said. Belarus is a long-time ally of Russia. Analysts describe the small country as Russia's "client state". Convoys have also entered the eastern Luhansk and Kharkiv regions, and moved into the Kherson region from Crimea - a territory that Russia annexed from Ukraine in 2014. The Russian offensive was preceded by artillery fire and there were injuries to border guards, the DPSU said. There have also been reports of troops landing by sea at the Black Sea port cities of Mariupol and Odesa in the south. A loud explosion has been heard in Odesa's city centre and a British resident of the city told the BBC many people were leaving. Deaths reported At least eight people are known to have died in bombings by Russian forces, Ukrainian police say. An attack on a military unit in Podilsk outside Odesa killed six people and wounded seven, officials say. Nineteen people are missing. One person died in the eastern city of Mariupol, they added.