This map shows the places where Russian explosions and attacks have been reported in Ukraine

(CNN Spanish) — Russia’s invasion of Ukraine began hours before dawn with a series of missiles targeting locations near Kyiv, as well as the use of long-range artillery against the northeastern city of Kharkiv, near the Russian border.

The attack quickly spread across central and eastern Ukraine as Russian forces attacked the country from three sides.

In the pre-dawn hours, people in the cities of Odessa, Dnipro, Mariupol and Kramatorsk reported huge explosions.

The world reacted to President Vladimir Putin’s decision to order a special military operation in the Donbas region of Ukraine.

United Nations Secretary-General Antonio Guterres urged Putin to return his troops to Russia and stop “what could be the worst war since the turn of the century.”

For his part, in a tweet early Thursday morning (local time), NATO Secretary General Jens Stoltenberg condemned Russia’s “reckless attack on Ukraine, which puts countless civilian lives at risk.”

After a few hours of calm in the morning local time, CNN crews in Kyiv, Kharkiv, Odessa and Mariupol reported hearing sounds of attacks again on Thursday, though so far they appear to be less severe than the explosions reported overnight.

On Thursday morning, air raid sirens sounded in the western Ukrainian city of Lviv for the first time, outside of regular drills, since World War II. Like clockwork, the quaint town has transformed from a tourist hotspot to a place gearing up for war.

The situation is very fluid, but this is what we know so far about Russia’s explosions and attacks in Ukraine.

Look at the places where the actions have been reported on this map: