NOVOLUHANSKE, Ukraine — “Be calm,” Denis, the 28-year-old driver said, after several mortar shells landed on the road behind us. As we sought cover inside the local army headquarters, another half-dozen mortar shells exploded around us.
We had been on a hastily arranged press tour to a tractor repair facility that had been struck by mortar fire just hours before. A Ukrainian commander pointed to two gaping holes left by the blasts, which he said had injured a 27-year-old soldier.
“This was a provocation” from the Russia-backed rebels on the other side of the border, the commander, Anatoly Semenko, said in an interview. He showed a video taken of the soldier’s arm bleeding, and said it would probably have to be amputated.
With that, Mr. Semenko said it was not safe for us to linger at the site, and as the small convoy of military vehicles departed, the shelling started again. As far as we could tell, there was no return fire from the Ukrainian forces.
It was not clear whether the press tour was targeted by the rebels. But another tour run by the Ukrainian military similarly ran into intense shelling in the town of Stanitsya Luhanska on Saturday.
Artillery fire picked up throughout eastern Ukraine Saturday, raining down all along the line of demarcation between Ukrainian and rebel-held territory. Rebel fire from mortars, artillery and rocket-propelled grenades was about twice that of the previous two days, the Ukrainian Ministry of Interior Affairs said in a statement.
The fight for the rhetorical high ground proceeded apace as well. In the separatist region, thousands of people were being evacuated across the border to Russia, purportedly in anticipation of a Ukrainian attack.
Ukrainian officials dismissed that as a propaganda gambit to give Russia a pretext to intervene. They warned in turn of “false flag” attacks by the separatists that the separatists would portray as terrorist attacks from Ukraine.
One of the evacuees, Inna Shalpa, said she had no idea where she and her three children were headed in Russian buses on Saturday, but she was certain they had to get moving. “We were mostly worried about the children,” she said.
Fed a steady diet of Russian state news reports, the crowds streaming into buses had little doubt a Ukrainian attack was imminent, something Ukrainian officials denounced as a fictional provocation.
From all appearances, most of the fire was directed toward eastern Ukraine from rebel forces. As shells rained down Saturday morning, Tanya Tinyakova stood in the doorway of her house in the village of Luhansk, in the thick of the barrage, weighing whether the time had come to pack up and go.
“When we are very nervous, we will leave,” she said. “But we built this house with our hands. We don’t want to leave. This is ours. We have no place to escape to.
“Even if we had a place to go, we don’t want to,” said Ms. Tinyakova, 31, “because this is our home.”
But Ms. Tinyakova and thousands like her soon may have no choice, as President Biden warned the world that a Russian attack was virtually certain within coming days. She and thousands of others nearby have the added misfortune of living in an area that has worried security analysts for weeks for its proximity to dangerous industrial infrastructure, including an important power station, a huge waterworks and a sprawling chemical plant.
The waterworks serves millions of people on both sides of the border, including residents of the city of Donetsk, one of the two rebel capitals. A cutoff of that water supply in fighting in 2014 had hastened an outflow of refugees from the city.
On Saturday, Russia’s Interfax news agency cited Eduard Basurin, a spokesman for the Donetsk People’s Republic, saying that shelling had damaged a pumping station and water pipes, and that the water supply was again at risk. The loss of water for residents in the Russian-backed areas came as a setback for Ukraine, reinforcing the Russian assertions of increasingly dire conditions for civilians.
But the greatest concern surrounded the chemical plant, which stands in rebel territory and is one of Europe’s largest producers of fertilizer. The fear is that a shell fired by Ukrainian forces in response to heavy rebel shelling from the vicinity of the plant might go astray. If it were to hit the pressurized tanks or the more than 12 miles of pipelines holding poisonous ammonia gas, it could produce a toxic cloud that could serve as an excuse for a Russian invasion.
Alternatively, the United States has warned that the Russian government could stage an incident with poisonous chemicals to justify intervention.
The Ukrainian Interior Ministry, which reports only incoming fire to government-held territory, said in its statement that 59 incoming mortar and artillery shells had landed in Svitlodarsk, the village closest to the plant, before 2 p.m. The shelling continued with another barrage at about 4 p.m.
Residents near Svitloldarsk said that both sides had been firing artillery in recent days.
Earlier on Saturday, the Ukrainian military said one soldier had been killed and another wounded in fighting along the frontline in the area, near the chemical plant and the waterworks.
Valerie Hopkins reported from Novoluhanske, Ukraine; Andrew E. Kramer from Severodonetsk, Ukraine, and Ivan Nechepurenko from Avilo-Uspenka, Russia.
