Donetsk, Ukraine (CNN) -- Two Ukrainian military jets were shot down Wednesday in the eastern part of the country, where pro-Russian rebels have fought against government forces, a Ukrainian military office said.
The pilots ejected, the office said. Information on their condition wasn't immediately available.
An air defense system shot down the jets after the pilots completed a task in Dmytrivka, a village in Ukraine's Donetsk region near the border with Russia, the military press office said.
Sergei Kavtaradze, an aide to rebel leader Alexander Borodai, the Prime Minister of the self-declared Donetsk People's Republic, told CNN that the two jets had been shot down by rebel fighters using a shoulder-fired missile system.
But Col. Andriy Lysenko, a spokesman for the Ukrainian National Security and Defense Council, said preliminary information suggested the missiles might have been launched from inside Russia.
The planes were flying at an altitude of 5,200 meters (17,000 feet) when they were hit, he said.
News of the jets' downing comes six days after the deadly crash of the civilian passenger plane Malaysia Airlines Flight 17 in eastern Ukraine.
The first of the bodies of the 298 victims of that crash arrived in the Netherlands on Wednesday, where they were met by family members, Dutch King Willem-Alexander and Queen Maxima and other dignitaries. About two-thirds of the victims were Dutch.
Ukrainian officials have previously accused pro-Russian rebels of shooting down several military aircraft.
In the week leading up to the July 17 crash of MH17, Ukrainian officials said an Antonov An-26 transport plane and a Sukhoi Su-25 fighter jet had been brought down. The Ukrainian military said the missile that struck the Su-25 had been fired from Russian territory.
The latest reported shootdown highlights the ongoing conflict in eastern Ukraine's Donetsk and Luhansk regions between the rebels and Ukrainian security forces.
A CNN team on the ground in Donetsk was turned away by rebel fighters at the entrance to the town of Snizhne, near Dmytrivka. The militants said they had orders not to allow people to travel farther because of fighting.
A jet could be heard passing periodically very high overhead, while on the ground, ambulances rushed past, as did a convoy of rebel fighters in civilian vans and cars.
Claim and counterclaim
Meanwhile, the finger-pointing continues over who was responsible for bringing down Flight MH17, a Boeing 777.
U.S. officials say pro-Russian rebels were responsible for shooting down that plane, but they say they now believe it's likely the rebels didn't know it was a commercial airliner, U.S. intelligence officials said Tuesday.
However, Vitaly Nayda, Ukraine's director of informational security, told CNN's Kyung Lah that the person who shot down the flight was "absolutely" a Russian. "A Russian-trained, well-equipped, well-educated officer ... pushed that button deliberately," he said.
Moscow has denied claims that it pulled the trigger. And Russian Army Lt. Gen. Andrei Kartapolov suggested a Ukrainian jet fighter may have shot the plane down. Ukraine's government rejects that claim.