ST. PETERSBURG, Russia — The Russian military was the source of a missile that shot down a civilian airliner over Ukraine four years ago, killing all 298 people aboard, prosecutors in the Netherlands said on Thursday in a finding certain to further sour relations between Russia and the West.

The stark determination by prosecutors, supported by video and photographic evidence, set the stage for a diplomatic standoff over how those responsible should be punished. It also increases the likelihood that prosecutors will hand down indictments of Russian military officers and soldiers, setting up a new confrontation with the Russian government.

The prospect of yet another stare-down with Moscow arrives at a moment when the West’s relations are already deeply strained.

Scores of Russian diplomats were expelled from Western nations in recent months over accusations that Moscow poisoned a former spy on British soil. Anger has mounted over Russia’s annexation of Crimea and its fomenting of rebellion in eastern Ukraine. And investigations have grown over its meddling in Western elections.

Even as Russia is still struggling under sanctions imposed for its annexation of the Crimean part of eastern Ukraine, its military intervention in Syria has again divided it from the West.

The Russian government has denied any role in shooting down the Boeing airliner over Ukraine. But it is improbable that anyone other than a senior Russian military commander could have ordered the sophisticated antiaircraft system deployed to Ukraine.

The missile belonged to an active duty unit in the Russian military, the 53rd Antiaircraft Brigade based in the city of Kursk, the prosecutors said. It was trucked from Russia to eastern Ukraine in July 2014, at a time when Russian-backed rebels were taking losses from Ukrainian airstrikes and artillery guided by airborne spotters.

Eastern Ukraine, though, was also a busy civilian air corridor for international flights. The missile struck Malaysia Airlines Flight 17, causing the worst single loss of life for civilians during the now four-year-old Ukraine war.

The airplane broke up in the sky and scattered debris and bodies over a wide area. During shaky truces negotiated to retrieve the bodies, Dutch and Australian emergency workers also found evidence of the crime. They removed missile fragments along with plane debris that were later used to identify the weapon. The missile, called a Buk, was made in Moscow in 1986, prosecutors said Thursday.

Western governments quickly blamed Russia, saying it had sent the missile launcher as military aid to the rebels. Russian officials and state news media have suggested a range of alternative theories, including that a Ukrainian military jet downed the airliner.

Multiple witnesses saw the missile launcher arrive in Ukraine from Russia on public roads, and The Associated Press reported its deployment into the war zone before the Malaysia Airline jet was shot down.

Two investigations carried out in the Netherlands have proceeded more slowly to reach the same conclusions, drawing on evidence gathered methodically in the ensuing years.

The plane was en route from Amsterdam to Kuala Lumpur, the capital of Malaysia, and a majority of the victims were Dutch citizens. The Dutch Safety Board, an investigating body, concluded in 2015 that a type of Russian missile known as a Buk had destroyed the Boeing 777.

The following year, the Joint Investigation Team, formed with prosecutors from Austria, Belgium, Malaysia, the Netherlands and Ukraine, traced the missile launcher’s route from Russia to Ukraine and back. It said then that it had narrowed a pool of suspects to about 100 people.

Australia’s foreign minister, Julie Bishop, issued a statement saying that “a sophisticated weapon belonging to the Russian Army was dispatched and used to shoot down a civilian aircraft.” This action, he said, “should be of grave international concern. We are discussing these findings with our partners and considering our options.”

Announcing the findings on Thursday in the Netherlands, Wilbert Paulissen, a criminal investigator with the country’s national police, said investigators had not determined whether soldiers from the Russian unit based in Kursk had also operated the system in Ukraine. Ukrainian separatists might have operated it. Mr. Paulissen said the pool of suspects had been narrowed to a few dozen people.

The Joint Investigation Team began its work after Russia vetoed a Dutch proposal to form a United Nations tribunal to study the disaster and punish those responsible.

The Russian government is unlikely to extradite any of its citizens or officers for trial in another country. The Russian Constitution prohibits the extradition of its citizens to face charges abroad.