By Peter Baker, Michael R. Gordon and Mark Mazzetti

New York Times News Service

AIDS researcher among victims — Dr. Joep Lange, 59, an AIDS researcher and the executive scientific director of the Amsterdam Institute for Global Health and Development, was among 298 passengers and crew aboard Malaysia Airlines Flight 17, which was apparently shot down over Ukraine on Thursday. The disaster claimed the lives of a number of people headed to the International AIDS Conference, scheduled to begin on Sunday in Melbourne, Australia, the International AIDS Society said Friday. The World Health Organization confirmed Friday that Glenn Thomas, 49, a communications officer, and Pim de Kuijer, 32, a Dutch AIDS activist and former European Commission diplomat, were also aboard the plane.

— New York Times News Service

WASHINGTON — The U.S. government has concluded that the passenger jet felled over Ukraine was shot down by a Russian-made surface-to-air missile launched from rebel-held territory and most likely provided by Russia to pro-Moscow separatists, officials said Friday.

While U.S. officials are still investigating the chain of events leading to the destruction of Malaysia Airlines Flight 17 on Thursday, they pointed to a series of indicators of Russian involvement. Among other things, military and intelligence officials said there was mounting evidence that a Ukrainian military plane shot down just three days earlier had been fired upon from inside Russian territory by the same sort of missile battery used to bring down the civilian jet.

The intelligence persuaded President Barack Obama to publicly lay responsibility at least indirectly at the door of the Kremlin. Speaking at the White House, he tried to channel international indignation toward Russia for what he called an “outrage of unspeakable proportions.” Obama said the episode should be “a wake-up call for Europe” and “should snap everybody’s heads to attention” about what is going on in Ukraine, where a pro-Russia insurgency has become an international crisis.

Without going into detail about the intelligence he had been shown, Obama said the separatists had been armed and trained “because of Russian support.” High-flying aircraft cannot be shot down without sophisticated equipment and training, he added, “and that is coming from Russia.”

He singled out President Vladimir Putin of Russia, accusing him of waging a proxy war that led to the tragedy. “He has the most control over that situation,” Obama said, “and so far, at least, he has not exercised it.”

Russia denied involvement and suggested that Ukraine’s military might have been responsible, an assertion Ukraine rejected. Putin called for talks, saying: “All sides to the conflict must swiftly halt fighting and begin peace negotiations. It is with great concern and sadness that we are watching what is happening in eastern Ukraine. It’s awful; it’s a tragedy.”

As investigators tried to sort out control of the crash site in the middle of a war zone and families mourned the victims, the global revulsion at the downing of the plane grew. European leaders joined Obama in calling for an international investigation unimpeded by combatants and talked about further steps against Moscow, including curbing arms sales.

While separatists guarding the crash site allowed some Ukrainian government rescue teams to enter and begin collecting bodies Friday, the Organization for Security and Cooperation in Europe said the armed rebels had prevented its monitors from gaining full access to the site in order to secure a safe route for the investigation and salvaging operations.

One rebel even fired into the air as the monitors were leaving, according to a spokesman for the organization, Michael Bociurkiw, who was there. Bociurkiw said bodies in the field were beginning to bloat. A separatist leader said the governments of the Netherlands and Malaysia had asked the rebels informally not to disturb the crime scene, but that there were not enough refrigerators to keep the bodies there.

U.S. intelligence agencies concluded that the Boeing 777-200 was struck by a Russian-made SA-11 missile fired from a rebel-controlled area near the border in Ukraine. U.S. analysts were focused on an area near the small towns of Snizhne and Torez, about midway between the rebel strongholds of Donetsk and Luhansk.

Their determination was based on an analysis of the launch plume and trajectory of the missile, as detected by a U.S. spy satellite. But the analysis did not pinpoint the origin of the missile launch or identify who launched it.