Pro-Russian rebels have shot down another Ukrainian Air Force's Su-25 Frogfoot fighter aircraft in the Luhansk region.
Ukrainian National Security and Defense Council spokesman Andriy Lysenko was quoted by 112.ua as saying: "Today a Su-25 attack aircraft has been shot down while on a combat mission.
"The fate of the pilot is unknown yet but hope remains that he will be alright."
The anti-government forces also struck two Ukrainian Mi-24 helicopters with portable air defence systems amidst heavy fighting in the city, as reported by CNN.
While one Mi-24 crashed, little is known about the fate of another helicopter and its pilot.
The Ukrainian Security Forces have reportedly regained control of a large part of Luhansk, following several days of street fighting and artillery attacks.
Luhansk has been without electricity, running water or phone connections for 18 days due to the ongoing fighting between the rebels and government forces, who have also tightened their encirclement of the neighbouring city of Donetsk.
Continued artillery attacks in Donetsk have killed 43 locals and injured 42 others in the last two days, according to media reports.
The Ukrainian Government has confirmed that the security forces have gained control of Ilovaysk, but nine soldiers were killed and 22 were wounded in the fighting.
According to UN, the Ukrainian conflict has killed more than 2,000 people and displaced more than 340,000 since its start in mid-April.
Meanwhile, the talks between the foreign ministers of Ukraine, Russia, Germany and France aimed at finding a solution to defuse Ukraine crisis on 17 August, ended without any success.
Russia has sent a 280-vehicle humanitarian aid convoy comprising water, food and medicine to suffering civilians in eastern Ukraine.
However, the Ukrainian and Western governments claim that the convoy might be a pretext for moving military supplies to insurgents, a charge which Moscow has consistently denied.
Image: A Su-25UB fighter aircraft of the Ukrainian Air Force. Photo: courtesy of Dima Sergienko.