"We will hand over 13 of our MiG-29 jets to Ukraine," Slovak Prime Minister Eduard Heger told journalists, adding that Bratislava would also deliver a Kub air defence system to Ukraine.

"We're giving these MiGs to Ukraine so that it can protect civilians against the many bombs that fall on their houses and which are the reason why people are dying in Ukraine," Heger said.

Poland on Thursday said Warsaw would send four Soviet-made MiG-29 jets to Ukraine "in the coming days".

Ukraine has long requested fighter jets from Western allies, although seeking primarily modern US-made F-16s.

"Our steps are fully coordinated with Poland and Ukraine," Heger said, adding that his government "stands on the right side of history".

Ukrainian President Volodymyr Zelensky thanked Slovakia on Friday for "a powerful package of air & air defense weapons, including MiG aircraft."

Ukraine recently declined to confirm to AFP the number of MiG-29s it has in operation, but according to the World Air Forces 2023 report by Flight Global released at the end of last year, the country operated 43 of the aircraft.

The Kremlin on Friday said the fighter jets given to Ukraine by Poland and Slovakia would be destroyed.

"The supply of this military equipment -- as we have repeatedly said -- will not change the outcome of the special military operation... Of course, all this equipment will be destroyed," Kremlin spokesman Dmitry Peskov told journalists, using the official term for Moscow's military intervention.

Heger said Slovakia will receive compensation for the donation from the European Peace Facility, the EU's Ukraine fund.

Slovak Defence Minister Jaroslav Nad also mentioned a US offer of a military system with a value of approximately $700 million, without providing details.

"We are talking about 900 million (euros) altogether," he added.

- 'Do more to help' -

Fellow staunch Ukraine supporter Estonia on Friday applauded the decision to send planes, saying Poland and Slovakia showed "great leadership".

"We need to do more to help Ukraine win and defeat the aggressor," Estonia's defence ministry added.

Nad said the transfer of MiGs from Slovakia to Kyiv will take "a couple of weeks".

The batch will include 10 operational MiG-29 fighter jets and an additional three that have not been operational since 2008.

Slovakia said at least three of the jets will only be used as spare parts.

Slovakia also has one other MiG-29 that will be placed in a military museum at home.

The country plans to replace the jets with American F-16s. The changeover should take place no later than January 2024.

Slovakia opted to stop using its MiGs last year since they were dependent on Russian technicians and companies.

The Czech Republic and Poland have since been protecting its airspace.

Following Poland's announcement, Ukraine said Thursday it was "grateful to our partners" though it added that "MiGs will not solve the tasks, we need F-16s".

The White House on Thursday said Poland's announcement did "not change" the US decision against sending its own F-16 warplanes to Kyiv.

On Friday, Spanish Defence Minister Margarita Robles also ruled out sending fighter planes to Ukraine.

"We are not going to send fighter planes, because the fighter planes that some of us have require a different level of training and preparation than those held by other countries like Poland," Robles said.