Scenes from Kharkiv: Battle wreckage, the boom of artillery, and people sheltering in the subway.

KHARKIV, Ukraine — The thuds of artillery start as a low-decibel rumble, but rattle the rib cage as you get closer. A crossroads at the northern entrance of Kharkiv is about as close to the front lines as anyone would wish to be on Friday, as Ukrainian soldiers waged a fierce battle to push Russian forces away from the city.

The empty carcasses of burned-out Russian armored personnel carriers and a Ukrainian police jeep littered the roadway, along with the scattered belongings of their former occupants — water bottles, a soldier’s boot, camouflage clothing. Nearby, the body of a Russian soldier, in a drab green uniform, lay on the side of the road, dusted in a light coating of snow that fell overnight.

The position was held, as of Friday, by a group of lightly armed Ukrainian soldiers who had hastily dug trenches into the wet mud beside the road, diving into them periodically when the artillery boom was especially loud.

Behind them, huge blue and yellow letters spelled KHARKIV, marking the entrance to Ukraine’s second-largest city, home to 1.5 million people, in the northeastern part of the country.

Whether the Russian troops in those destroyed armored carriers had meant to enter the city was unclear, as were the intentions of their comrades fighting what sounded like a vicious battle just beyond a line of trees in the distance. They had pushed into the region a day earlier, having traveled some 40 miles from their staging area near Belgorod in Russia.

The Ukrainian soldiers sent to hold the position had few details of the fight that took place there, saying only that it happened Thursday morning, shortly after Russia’s president, Vladimir V. Putin, gave the order to attack.

“Putin wants us to throw down our weapons,” said a Ukrainian soldier named Andrei, from inside a muddy trench. “I think we could operate more slyly, gather up our forces and launch a counterattack.”

Most of the fighting appeared to be taking place a few miles outside the city limits, near a village called Tsyrkuny.

The number of military and civilian casualties resulting from the fight was unclear, but on Friday the local police said a 14-year-old boy had been killed in a village near Kharkiv when a shell hit near his home. But strikes occasionally hit close enough to the city to elicit shrieks of terror from pedestrians, sending them fleeing into metro stations for cover.

Inside an underground station in central Kharkiv, terrified residents have been holed up for two days with their babies, pets and the few belongings — blankets, yoga mats and spare clothing — they could grab in short dashes to home and back, during breaks in the shelling. The city has parked trains in the station and allowed people to sleep in them.

Lidiya Burlina and her son, Mark, work in Kharkiv and were cut off from their home village, a two-hour train ride away, when the Russians moved in. They’ve been living in the metro station ever since. The stores in town are working only in the morning, Ms. Burlina said, and there is very little bread, which has dramatically increased in price in the two days since the war started. They cannot reach anyone in their village because the local power station was blown up.

“They’re sitting there in the cold, they can’t buy anything, and there’s no heat,” Ms. Burlina said. “And we’re here in the metro.”

Victoria Ustinova, 60, was sheltering in the metro with her daughter, two grandchildren and a fuzzy Chihuahua named Beauty, who was wearing a sweater. The family could have taken shelter in the basement of their apartment building, but from there the booms of artillery and tank fire were still audible.

“When everything started it was a total shock, when you don’t know where to run and what to expect from ‘the comrade,’” Ms. Ustinova said, referring to Mr. Putin. “Now we’ve already settled down. We’ve have accepted it and are trying to continue living. It was worse during World War II.”

For her 13-year-old grandson, Danil, the main worry now is the potential for World War III.

“If things will become totally inflamed, then Europe will join in, and if they start launching nuclear weapons then that’s it,” he said.

Up on the surface, most of the stores and restaurants were closed and few people walked the streets. One of the few exceptions was Tomi Piippo, a 26-year-old from the Finnish city of Iisalmi, who said he came to Kharkiv on holiday on Monday and now couldn’t get out.

“I don’t know how to leave. No planes,” he said.

While Russian officials have said their military was endeavoring to avoid civilian areas, the body of a Smerch rocket, which Ukrainian officials said was fired by Russian forces, was stuck vertically in the middle of the street outside the headquarters of the National Guard. A few kilometers away, the rocket’s tail section had buried itself in the asphalt across from an onion-domed Orthodox church.

A team of emergency services officers, dressed in flack jackets and helmets, was attempting to extract the tail from the pavement, but having difficulties. A member of the team said that the tail and the body were different stages of the rocket, likely jettisoned as the explosive ordnance hurtled toward its target near the front lines.

“This is 200 kilos of metal,” the emergency officer said, pointing to the rocket’s tail. “It could have fallen through a building or hit people.”

Even as the artillery barrages intensified, not everyone was ready to hide. Walking with intention toward the source of the artillery booms on the outskirts of Kharkiv was Roman Balakelyev, dressed in camouflage, a double-barreled shotgun slung over his shoulder.

“I live here, this is my home. I’m going to defend it,” said Mr. Balakelyev, who also pulled out a large knife he had strapped to his back as if to show it off. “I don’t think the Russians understand me like I understand them.”

A short while later, Mr. Balakelyev reached the edge of the city, where the Ukrainian troops were huddled around the abandoned Russian troop transports. They watched as he passed. No one moved to stop him. One soldier uttered: “Intent on victory.”

Mr. Balakelyev, his gaze fixed and his shotgun ready, headed down the road in the direction of the booms and a tall billboard that read: “Protect the future: UKRAINE-NATO-EUROPE.”