LVIV, Ukraine (AP) — Russia widened its offensive in Ukraine on Friday, striking airfields in the west and an industrial city in the east for the first time, while the huge armoured column stalled for over a week outside Kyiv was on the move again, spreading out into forests and towns.

The US and its allies prepared to step up their efforts to isolate and sanction Russia by revoking its most favoured trading status. But with the invasion now in its 16th day, Russia appeared to be trying to regroup and regain momentum, with expanded bombardment and tightening of its stranglehold on cities already under attack, particularly the strategic port of Mariupol, where tens of thousands struggled to find food amid an intense, 10-day-old siege.

Russian President Vladimir Putin said there have been “certain positive developments” in Russia-Ukraine talks but gave no details. He told Belarus’s leader that negotiations were being held “almost on a daily basis”.

In the meantime, Ukrainian President Volodymyr Zelenskyy said Ukrainian forces had “reached a strategic turning point”, though he did not elaborate.

“It’s impossible to say how many days we will still need to free our land, but it is possible to say that we will do it,” he said via video from Kyiv.

He also said authorities were working on establishing 12 humanitarian corridors and trying to ensure food, medicine and other basics get to people across the country.

Western and Ukrainian officials have said Russian forces have struggled in the face of stiffer resistance and heavier losses than anticipated, along with supply and morale problems. So far, they have made the biggest advances on cities in the south and east while stalling in the north and around Kyiv.

Friday’s strikes targeted the west, away from the main battle zones. Russian Defence Ministry spokesman Igor Konashenkov said Russia used high-precision, long-range weapons to put military airfields in Lutsk and Ivano-Frankivsk “out of action”.

The Lutsk strikes killed four Ukrainian servicemen and wounded six, Lutsk Mayor Ihor Polishchuk said. In Ivano-Frankivsk, residents were ordered into shelters in an air raid alert

Russian airstrikes also targeted for the first time the eastern city of Dnipro, a major industrial hub and Ukraine’s fourth-largest city, situated on the Dnieper River. Three strikes hit, killing at least one person, according to Ukrainian Interior Ministry adviser Anton Heraschenko.

In images of the aftermath released by Ukraine’s emergency agency, firefighters doused a flaming building, and ash fell on bloodied rubble. Smoke billowed over shattered concrete where buildings once stood.

In another potentially ominous development, new satellite photos appeared to show the massive Russian convoy outside the Ukrainian capital had fanned out.

Howitzers were towed into position to open fire, and armoured units were seen in towns near the Antonov Airport north of the city, according to Maxar Technologies, the company that produced the images.

The 40-mile (64-kilometre) line of tanks and other vehicles had massed outside Kyiv early last week. But its advance had appeared to stall amid reports of food and fuel shortages and attacks by Ukrainian troops with anti-tank missiles.

The purpose of the latest move was unclear, though Russia is widely expected eventually to try to encircle the capital.

Britain’s Ministry of Defence said that after making “limited progress”, Russian forces were trying to “reset and re-posture” their troops, gearing up for operations against Kyiv.

But Nick Reynolds, a land warfare analyst at British defence think tank Royal United Services Institute, said the move, in part, looks like an attempt by the troops to better protect themselves by dispersing. He said it may indicate that the Russians are not ready to surround the city quickly.

In the meantime, Russia is increasing bombardments and regrouping its forces on the ground.

“It’s ugly already and it’s going to get worse,” Reynolds said.

Moscow also indicated it plans to bring fighters from Syria into the conflict. Defence Minister Sergei Shoigu said Russia knew of more than 16,000 applications from Middle East countries, many of them from people who had had helped Russia against the Islamic State group.

Since 2015, Russian forces have backed Syrian President Bashar Assad against various groups opposed to his rule, including the Islamic State.

On the sanctions front, revoking Russia’s “most favored nation” trade status by the US and other nations would allow higher tariffs on some Russian imports. Western sanctions have already dealt a severe blow to Russia, causing the ruble to plunge, foreign businesses to flee and prices to rise sharply. Putin has insisted Russia can endure sanctions.

In Syria, Russia backed the Government in imposing long, brutal sieges of Opposition-held cities, wreaking heavy destruction and causing widespread civilian casualties. That history, along with the siege of Mariupol, has raised fears of similar bloodshed in Ukraine.

Temperatures sank below freezing across most of Ukraine and were forecast to hit -13 degrees Celsius (8 Fahrenheit) in the eastern city of Kharkiv, which has come under heavy bombardment.

Some 400 apartment buildings in Kharkiv lost heat, and Mayor Ihor Terekhov appealed to remaining residents to descend into the subway or other underground shelters where blankets and hot food were being distributed.

The bombardment continued in Mariupol, where a deadly strike on a maternity hospital this week sparked international outrage and war-crime allegations. Repeated attempts to send in food and medicine and evacuate civilians from the city of 430,000 have been thwarted by continued attacks, and Ukrainian Deputy Prime Minister Iryna Vereshchuk put the number of dead there at more than 1,300.

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