Ukraine’s president, Volodymyr Zelensky, vowed to remain in Kyiv even as missiles pounded the capital and Russian forces pushed inward on Friday.
He also signed a decree on the general mobilisation of the population on Thursday, a day after the country started conscripting reservists aged between 18 and 60.
Mr Zelensky had ruled out a general mobilisation on Tuesday but Ukraine’s defence ministry reversed that stance in a statement on Friday.
“Today Ukraine needs everything,” the ministry quoted Yuri Galushkin, the commander of the troop forces, as saying in the statement.
The barriers to entry were low, with volunteers told to “carry only your passport and identification code. There are no age restrictions”.
Ukraine has also prohibited men between the age of 18 and 60 from leaving the country.
Its border authority said the restriction will last for the duration of martial law, which the president imposed shortly after Russia launched a full-scale attack.
“We have been left alone to defend our state,” Mr Zelensky said in a video address to the nation after midnight.
“Who is ready to fight alongside us? I don’t see anyone. Who is ready to give Ukraine a guarantee of Nato membership? Everyone is afraid,” he added.
“[The] enemy has marked me down as the number one target,” he said. “My family is the number two target. They want to destroy Ukraine politically by destroying the head of state.”
“I will stay in the capital. My family is also in Ukraine.”
Among those staying to fight were the Klitschko brothers, Wladimir and Vitali.
Mr Zelensky, who spoke with British prime minister Boris Johnson during the day, has also demanded tougher sanctions and support in fending off the aggressor marching toward Kyiv.
The country has so far lost at least 137 citizens, including military personnel, Mr Zelensky had announced, while according to British defence secretary Ben Wallace, more than 450 Russian troops have been killed in the fierce resistance by Ukrainian forces, implying that Moscow “failed” on its main objective on the first day of fighting.
