(NewsNation) — Air raid sirens could be heard in the western city of Lviv Saturday morning as Russia advances further in Ukraine.

New commercial satellite images appeared to capture artillery firing on residential areas between Russian forces and the capital. The images from Maxar Technologies showed muzzle flashes and smoke from the big guns, as well as impact craters and burning homes in the town of Moschun, outside Kyiv, the company said.

Ukrainian President Vladimir Zelenskyy blasted Russia for allegedly abducting the mayor of Melitopol, Ivan Fedorov.

“Obviously, this is a sign of the weakness of the invaders,” he said in his daily address.

Russia’s forces appeared to be trying to regroup and regain momentum after encountering heavier losses and stiffer resistance than anticipated over the past two weeks. Britain’s Ministry of Defense said Russia is trying to “re-set and re-posture” its troops, gearing up for operations against Kyiv.

“It’s ugly already, but it’s going to get worse,” said Nick Reynolds, a warfare analyst at Royal United Services Institute, a British think tank.

Friday, Putin approved using thousands of Middle-Eastern mercenaries, many coming from Syria. The Russian army has been in that country since 2015, which has helped Syrian President Bashar Assad fend off a civil war.

“It seems he’s reaching deeper into the bench to attempt to generate some combat power from mercenaries,” Jennifer Cafarella, chief of staff of the Institute for the Study of War, said on “NewsNation Prime” Friday.

With the invasion in its 17th day, Putin said there had been “certain positive developments” in Russia-Ukraine talks, but gave no details.

Zelenskyy also referenced a path to victory in his speech, but did not elaborate. Some ordinary citizens in Ukraine now believe they can expel the Russian troops.

“We don’t have that fear, which was in first days,” Nazar Zinchuk, a student at the Franko National University of Lviv, said on “NewsNation Prime.” “Now we see that we can fight and that we are winning this war. So even if Europe doesn’t want to help us, even if America is still silent, we are ready to fight this war.”

But the reality may trump the Ukrainians’ will. By some U.S. estimates, the Russians are running 20 times the number of sorties as the Ukrainians, the Associated Press reported. A sortie is an attack made by troops originating from a defensive position.

Some 2.5 million people have fled Ukraine since the invasion began, according to the United Nations.