As rescuers sift through the rubble of a Kramatorsk restaurant, distraught relatives wait for news.

KRAMATORSK, Ukraine — Rescuers were combing through the rubble in Kramatorsk on Wednesday as the death toll from a Russian missile strike on a popular restaurant in the eastern Ukrainian city climbed.

The missile tore into the crowded Ria Lounge restaurant at dinnertime on Tuesday, setting off a large blaze that burned for more than two hours. By Wednesday evening, the Ukrainian authorities said that 11 people had been confirmed dead — including 14-year-old twin sisters — and 61 others were wounded.

With search and rescue efforts ongoing, Ukraine’s intelligence agency, the S.B.U., said it had detained a man who allegedly helped direct the missile strike. It accused the man — described as a Kramatorsk resident working for a local gas transportation company — of sending video footage of the restaurant to Russian military intelligence. The S.B.U. did not name the person and the accusations could not be independently verified.

The restaurant’s terrace was a mess of overturned black-and-white sofas on Wednesday morning. As a crane lifted debris off a large pile of twisted rubble, distraught friends and relatives of people still missing waited anxiously behind police ribbon across the street. The restaurant’s owner paced while talking on her phone.

One woman was awaiting news of her niece. A man was seeking information about his brother-in-law. When emergency workers came out to take breaks, pouring water onto their heads to wash off the dust, people rushed over to ask them for updates — with one man showing a photo of his missing relative on his phone.

As two more bodies were pulled from the rubble, people strained to get a glimpse to see whether they were their loved ones. But the body bags were zipped tightly, and an emergency car quickly took them to the morgue.

Ria Lounge, known to many as Ria Pizza, was a long-running haunt in Kramatorsk and was particularly popular in the summer because of its covered outdoor seating. The restaurant, which was on the ground floor, had closed after Russia’s full-scale invasion of Ukraine began in February last year but reopened several months later. It is close to the Hotel Kramatorsk, which was badly damaged in a Russian attack last summer.

Ukrainian soldiers stationed nearby, some of them newly returned from the front, are frequent patrons, along with local residents, foreign journalists and aid workers.

Petro Golub, 66, said he had been sitting on a bench near the restaurant when he heard what sounded like a plane before an explosion. The blast wave threw him “all the way back,” Mr. Golub said.

“I am fine, fine, just little things — my legs were slashed by glass shards,” he said on Wednesday.

Kramatorsk, in the Donetsk region of eastern Ukraine, was home to 150,000 people before the war, but many have fled as Russia has set its sights on taking the whole region. It is far enough away from the front line for life to seem relatively normal on most days, but air raid sirens are common, and the sounds of distant artillery are sometimes heard.

It has been hit with a devastating attack before: A Russian missile strike hit a packed train station in April, killing more than 50 people. And the city featured heavily in Russia’s monthslong campaign to take the city of Bakhmut, serving as a way station for Ukrainian troops rotating out of the grueling fight.

Bakhmut’s capture by Russian forces in May left Kramatorsk under a greater threat and facing an increased risk of shelling. Ukrainian officials had also warned that Bakhmut’s fall could have a domino effect, clearing the way for Russian forces to advance on Kramatorsk, the city of Sloviansk and the rest of Donetsk.