"There will be general mobilisation in the (separatist) Donetsk People's Republic in 10 days' time, we plan on mobilising up to 100,000 men," Alexander Zakharchenko told the separatist news agency DAN.
The declaration came after the separatists vowed to push their offensive to take over the entirety of the Donetsk and Lugansk regions and the latest bid to establish a ceasefire collapsed.
Fighting has since intensified, with Kiev officials and local authorities saying today that five Ukrainian soldiers and three civilians had been killed in clashes in the last 24 hours.
Two civilians, both men, were killed in a rebel Grad rocket strike in the village of Krimske, around 40 kilometres northwest of separatist centre Lugansk, regional pro-Kiev governor Gennadiy Moskal said.
Also Read
Another man was killed in firing overnight in the other main rebel centre Donetsk, city authorities said.
An AFP journalist in the city said firing in Donetsk continued into the night, but was less intensive today morning.
Fighting in east Ukraine claimed around 50 lives over the weekend, with the latest attempt at truce talks collapsing in Minsk yesterday.