At the moment Ukrainian citizens who are currently crossing the Lithuanian border need to have only an identity document. They are allowed to live for 1 year in the country.
Useful links
Electronic migration services:
https://www.migracija.lt/app/form-wizard?nationality=UKR
Migration Department under the Ministry of the Interior of the Republic of Lithuania. Hotline for Ukrainians:
Consultations are provided by phone No. +370 5 271 7112
Available 7 days per week from 07:30 am until 21:00 pm
More info here
Migration services
8 707 67000 - for people in Lithuania
+370 5 271 7112 - for people abroadinfo@migracija.gov.lt