Deputy PM Andriy Klyuyev said the initial toll had risen after rescue workers found a further six bodies in the remains of the 10-storey building.
Seven children died in the blast, while another 16 people were hospitalised.
Prosecutors believe the explosion happened because valves regulating pressure in the gas pipes had worn out.
Three employees of the local Dniprohaz gas company have been detained by the authorities pending potential negligence charges.
However, Gazex, a Russian company which controls Dniprohaz, has protested its employees' innocence.
"The guilty party should be determined once the results of the expert assessment have been released," a representative told the Russian Itar-Tass news agency.
Correspondents say domestic gas explosions occur regularly in Ukraine, often caused by improper use or poorly maintained infrastructure.
Source: BBC News