President Volodymyr Zelensky has told Ukrainians they have "withstood the blow" of Russia's invasion as he urged citizens to continue fighting.
In an impassioned speech delivered from Kyiv on Saturday night, Mr Zelensky told the country that the time has come for them to launch a fightback.
"You need to go out and drive this evil out of our cities," he said.
But the rallying cry came alongside a plea to US President Joe Biden to source more combat jets for Ukraine.
US officials are believed to be in discussions with political leaders in Poland over the possibility of Warsaw providing Ukraine with a number of MiG fighter jets.
Poland has been slowly phasing the Soviet-era fighter out of use and officials are understood to be weighing whether to provide them to Ukraine, where pilots are not trained to fly Western-made jets. Some reports suggest they could be exchanged for new US-sponsored replacements.
The news comes as the Russian invasion of Ukraine enters its 11th day, as some experts suggest the invasion may have stalled in places - despite President Vladimir Putin's insistence during a speech on Saturday that the operation is "going to plan."
While fighting has continued in many parts of the country, Moscow's forces have only captured one major Ukrainian city, Kherson - though it has made other key advances, such as seizing the Zaporizhzhia nuclear power plant on Friday.
Outside the capital of Kyiv, a massive convoy stretching out over 40 miles (64km) remains stalled outside the city and Ukrainian defence officials say they have been hitting selected targets within the convoy where they can. Elsewhere:
- There has been intense fighting to the north-west of Kyiv, where Russian troops have been attempting to re-take the strategic Hostomel airfield
- Moscow's forces have also been bombarding Irpin, a small town on the outskirts of Kyiv
- Ukrainian officials say a ceasefire agreed to allow civilians to escape from the city of Mariupol lasted for less than 30 minutes before shelling resumed
- Kharkiv and Sumy in the east have also come under renewed bombardment
- Russia said it has advanced by 7km (four miles) in the Donbass region, taking several towns and villages
- In Kherson, the only major city to have changed hands, there are reports of Russian troops firing on protesters to break up an anti-Russian demonstration
The head of the UN's refugee agency told Reuters that the number of refugees fleeing the Russian invasion could rise to 1.5 million by the end of the weekend.
"This is the fastest moving refugee crisis we have seen in Europe since the end of World War Two," UNHCR head Filippo Grandi said.
As fighting rumbles on in Ukraine, Western sanctions continue to hammer the Russian economy.
On Saturday night, the payments giants Visa and Mastercard both announced that they will withdraw their services from Russia, with Visa's chief executive Al Kelly saying in a statement that the company had been "compelled to act following Russia's unprovoked invasion of Ukraine, and the unacceptable events that we have witnessed".
The move means Russian banks will no longer be supported by the companies networks, and any cards issued outside of country will stop working at Russian merchants or ATMs.
But Sberbank, the country's largest lender, emphasised that Russians will be able to withdraw cash, make transfers, pay both in offline stores and Russian internet stores because transactions in the country pass through the domestic National Payment Card System, which does not depend on foreign payment systems.