Ukraine is expecting Russia to launch a major offensive in the east of the country "soon", Ukrainian defence ministry spokesman Oleksandr Motuzyanyk has warned.
"The enemy has almost finished preparation for assault on the east, the attack will begin soon," Motuzyanyk said at a briefing on Monday.
Ukraine's armed forces were bracing on Monday for a new Russian offensive as powerful explosions rocked cities in the south and east.
Ukrainian President Volodymyr Zelensky kept up his tireless campaign to generate international support and rally his countrymen, warning the coming week would be important and tense.
"Russia will be even more afraid. It will be afraid to lose. It will fear that the truth will have to be acknowledged," Zelensky said in a late-night video address.
"Russian troops will move to even larger operations in the east of our state. They may use even more missiles against us, even more air bombs. But we are preparing for their actions. We will answer."
Air raid sirens were heard across Ukraine early on Monday.
Russian forces were continuing their offensive to establish full control over the southern city of Mariupol, seeking to storm an iron and steel plant and the seaport, Ukraine's armed forces said.
Russia's invasion has forced about a quarter of Ukraine's 44 million people from their homes, turned cities into rubble and killed or injured thousands.
It has failed to take any major cities, but Ukraine says Moscow has been gathering its forces in the east for a major offensive and has urged people to flee.
A series of powerful explosions were heard in Ukraine's northeastern city of Kharkiv and in Mykolaiv, near the Black Sea in the southern part of the country, Ukrainian media reported on Sunday.
Earlier, missiles destroyed the airport in the city of Dnipro, said Valentyn Reznichenko, governor of the central Dnipropetrovsk region.
The New Arab is providing live updates of what's been happening on the ground and additional analysis on the conflict's significance.