KIEV, Ukraine — The quest for clues in the downing of a Malaysia Airlines jet faced major obstacles Friday as the pro-Russia militias that Ukraine blames for the disaster limited access to the crash site strewn with airplane parts and bodies.
Ukrainian officials were trying to negotiate safe passage for investigators and international observers deep in territory held by the pro-Russia separatists in the east of the country.
The fate of the airplane’s black-box data recorders, which could give crucial information about the plane’s final moments, was unclear, with neither side acknowledging possession.
Rebels argued among themselves whether to agree to a brief cease-fire to allow the bodies of victims to be taken to morgues elsewhere in the country.
Rebel leaders said they would leave victims and airplane parts in place to facilitate the investigation and vowed to allow investigators to visit the site because, they said, they had nothing to hide in the catastrophe in which 298 people died.
Ukrainian officials moved swiftly Friday to link the plane disaster to the rebels, saying that the Boeing 777-200 had been downed by separatists using a surface-to-air missile, possibly with direct Russian aid.
In Washington, President Obama said U.S. intelligence indicates that a Russian-made missile downed the plane from rebel territory, but he stopped short of saying who pulled the trigger.
“Nearly 300 innocent lives were taken — men, women, children, infants who had nothing to do with the crisis in Ukraine,” Mr. Obama said. “Their deaths are [an] outrage of unspeakable proportions.”
Ukrainian Prime Minister Arseniy Yatsenyuk echoed that sentiment in an address posted on his Web site.
“This is a crime against humanity. All red lines have already been crossed,” he said. “After these terrorists shot down a Malaysian Airlines aircraft, this is a war against the world.”
Rebel leaders and Russian officials denied any connection to the crash.
In Moscow, Russian Foreign Minister Sergei Lavrov said Friday that Ukrainian authorities bore broad responsibility for creating conditions in which citizens were moved to rebellion.
He did not suggest that the Ukrainian military had shot down the plane.
“What happened with the aircraft should make us stop, look back, and reflect” on the situation that began when Russia-friendly President Viktor Yanukovych was ousted in February, Mr. Lavrov said.
The extensive debris zone includes not only a wheat field where most of the plane was found but also nearby villages. Witnesses described looking across fields of sunflowers only to be jolted by the discovery of body parts on the ground.
The recovery efforts were moving slowly amid the civil conflict. Each step forward brought new tensions.
The Organization for Security and Cooperation in Europe, the Vienna-based organization coordinating a dialogue in the conflict, sent a group of 30 observers to the crash scene Friday, said Shiv Sharma, a spokesman.
The monitors were given access to the site for 75 minutes, and while they were at the heavily guarded site, rebels fired weapons into the air, Mr. Sharma said.
“The shots were not targeting the monitors as such; they were just into the air. It was not a particularly tense situation in which monitors were concerned about their security,” he said.
But the U.S. State Department said in a Twitter message Friday that monitors “were only granted limited access” to the crash site.
“They must have complete unfettered access,” the message said.
The observation team is negotiating on a day-to-day basis for time at the site.
Its job is to secure the crash scene until independent investigators arrive to help transfer bodies. As of Friday, 181 bodies had been found, according to a Ukrainian foreign ministry official, Andrii Sybiga.
The international team, which includes FBI and National Transportation Safety Board personnel from the United States, was expected to re-enter the area over the weekend.
The rebel leaders were divided over whether to agree to a cease-fire to allow for a fuller international presence at the scene. By day’s end, separatist leader Alexander Borodai said no truce talks were being held and another rebel leader, Denis Pushilin, announced from Moscow that he was resigning from leadership, the Interfax news agency reported.
Violence has continued, particularly in Ukraine’s Luhansk region, said Andriy Lysenko, spokesman for Ukraine’s National Security and Defense Council. Ukrainian forces were attacked at checkpoints 19 times Thursday and Friday, he said.