Ukraine’s military blamed pro-Russian separatists of shooting down the MiG-29 jet on Sunday morning, close to the Russian border.
Military spokesman Oleksiy Dmytrashkivsky told Al Jazeera the aircraft was downed around the city of Luhansk after carrying out an attack on rebels.
The military said the pilot had ejected and had been found alive and well after a search.
Hours later, Ukraine’s military spokesman said a convoy of rocket launchers had crossed over from Russia in the past 24 hours.
Andriy Lysenko accused Russia of sending over three Grad missile systems, and Russian drones of violating Ukrainian air space on 10 occasions.
He also said on Sunday that the government forces fought separatists in a neighbourhood of Luhansk city on Saturday and took control of the Zhovtneviy neighbourhood police station.
“They raised the state flag over it,” Lysenko told a news briefing.
Al Jazeera’s Emma Hayward, reporting from the Ukrainian town of Novotroyitske, said that despite Ukrainian forces making several advances into rebel-held territory, it looked like the separatists still held considerable fire-power.
The flashpoint Luhansk is encircled by Ukrainian forces and is reportedly suffering from severe electrical outages and shortages of food and medicine.
Fleeing residents told Human Rights Watch there was no gas and mobile phone coverage in the city, and it was difficult finding drinking water and food.
Donetsk, the largest rebel-held city, is also suffering frequent fighting including shelling.
The city’s mayor said at least 10 civilians were killed and eight injured during heavy artillery shelling on Saturday.
The foreign ministers of Ukraine and Russia are to meet in Berlin on Sunday to resume diplomatic talks on a political solution to the crisis in eastern Ukraine.
Fighting in Ukraine has escalated since the insurgency arose in April, with government troops steadily taking back rebel-held territory in the east.