Oleg Babayev, mayor of the central-eastern city of Kremenchuk was killed not far from his home, the interior ministry said.
In the other attack, the house of Andry Sadovy, mayor of the western city of Lviv, was hit by a rocket fired yesterday.
No one was in the house at the time of the strike, his office said in a statement as local police launched a probe into what they described as a "terrorist attack".
"To my knowledge, no rocket launchers have been used to fire shots in Lviv," said Sadovy.
Lviv, a city with a population of 750,000 close to the Polish border, is a nationalist bastion of Ukrainian-speakers.
Both Lviv and Kremenchuk have been spared from the violence plaguing eastern Ukraine, where pro-Russian separatists are locked in a deadly battle against Ukrainian forces.
