LONDON — A day after investigators identified the Russian military as the source of a missile that brought down a civilian airliner over Ukraine four years ago, the Netherlands and Australia, whose citizens made up the vast majority of passengers on the jet, said on Friday that they would hold Moscow to account for bringing down the plane.
The Dutch authorities said in a statement that they had “asked Russia today to enter a dialogue in order to come to a solution that does justice to the enormous suffering and damage caused by the downing of” Malaysia Airlines Flight 17, which was traveling to Kuala Lumpur from Amsterdam.
The two countries’ demand received support later in the day from the State Department, which called on Russia to cease what it called a “callous disinformation campaign,” but the practical outcome of such diplomacy is unclear at a time of profound strains between Russia and the West.
The disputes cover a broad range of issues, including the poisoning of a former Russian spy in Britain and suspicions that Moscow has sought to manipulate the outcome of Western elections, including President Trump’s victory in 2016.
The latest developments came after an international team of investigators said on Thursday that the missile that brought down the plane as it passed over Ukraine had originated with an active duty Russian military unit, the 53rd Antiaircraft Brigade. Among the 298 people on board the jet were 196 Dutch citizens and more than three dozen citizens and residents of Australia.
The missile was brought into eastern Ukraine in July 2014, when Ukrainian forces were inflicting losses on Russia-backed rebels, the investigators said.
“Based on these findings, the only conclusion we can reasonably now draw is that Russia was directly involved in the downing of MH17,” the Australian Foreign Ministry said in a statement.
The conclusions were in line with a finding in 2015 by the Dutch Safety Board, an investigating body, that the plane had been destroyed by a missile known as a Buk, but went further in identifying the role of a Russian military unit.
“The government is now taking the next step by formally holding Russia accountable,” the Dutch foreign minister, Stef Blok, said in The Hague, although the authorities were quick to note that such a task would be difficult.
In a statement, the Dutch cabinet acknowledged that “Holding a country responsible is a complex legal process.” But, the statement added, “This is the legal avenue that the Netherlands and Australia have now chosen to pursue.”
Russia has repeatedly rejected the Western charges and has long insisted that it had no part in the shooting down of the plane. On Friday, Dmitri S. Peskov, the Kremlin spokesman, said that Russia “absolutely” denied involvement.
The investigators refrained from blaming Russian soldiers directly for firing the missile, which could have been launched by Ukrainian separatists.
Debris from the attack — the worst single act of bloodletting during the now four-year-old Ukraine war — was strewn over a wide area. Dutch and Australian emergency workers found missile fragments and detritus from the Boeing 777 that were later used to identify the weapon.
The plan by the Dutch and Australian authorities comes as Moscow is trying to cope with onerous sanctions imposed as punishment for annexing Crimea, its support of separatists in eastern Ukraine and meddling in the United States presidential election.
The role played by President Vladimir V. Putin in supporting President Bashar al-Assad in Syria against Western-backed rebels has also set Moscow against the West in a multifaceted confrontation that has prompted some Westerners to speak of a new Cold War.
Separately on Friday, Bellingcat, an investigative group that conducts research with open-source information, said it had identified a second high-ranking Russian military intelligence commander said to have been active in eastern Ukraine at the time the plane was brought down.
The group, which includes professional journalists in Moscow and Washington, identified the officer as Oleg V. Ivannikov, and said he operated under the nom de guerre Andrei I. Laptev and the code name Orion.
Part of his job in eastern Ukraine in 2014 was to supervise “the procurement and transport of weapons across the Russia-Ukraine border,” Bellingcat said. “He held these functions at the time of the downing” of the Malaysian airliner, it said.
According to a report by the same group in December, the person code-named Orion was heard in a telephone intercept discussing the movement of military equipment with another Russian, who had the code-name Delfin. The group identified Delfin as a semiretired Russian three-star general, Nikolai F. Tkachev.
Follow Alan Cowell on Twitter: @cowellcnd
Andrew E. Kramer contributed reporting from St. Petersburg, Russia.