"Mom, hang in there," exclaimed a weeping woman who was fleeing Shakhtarsk with her mother. Associated Press reporters saw a high-rise apartment block in the town being hit by at least two rounds of artillery.
The fighting there and elsewhere in the area kept Dutch and Australian police for the second day from reaching the site where the plane crashed after being shot from the sky. They had planned to begin searching for remaining bodies and gathering forensic evidence and the delay strained tempers among international observers.
"There is a job to be done," said Alexander Hug, the deputy head of a monitoring team from the Organization for Security and Cooperation in Europe. "We are sick and tired of being interrupted by gunfights, despite the fact that we have agreed that there should be a ceasefire."
The plane was downed on July 17 while flying over a part of eastern Ukraine where government forces and pro-Russia separatist rebels have been fighting for months. Ukrainian and Western officials say the plane was shot down by a rebel missile, most likely by mistake, and that Russia supplied the weapon or trained rebels to use it. Both the rebels and Moscow deny that.
A Ukrainian official said Monday that data from the recovered flight recorders show that Malaysia Airlines Flight 17 crashed due to a massive, explosive loss of pressure after being punctured multiple times by shrapnel. Andriy Lysenko, spokesman for Ukraine's national security council, said the plane suffered "massive explosive decompression" after it was hit by fragments he said came from a missile.
There were signs that government forces were gaining some ground in their fight with the rebels.
Ukraine's Defense Ministry said Ukrainian troops entered Shakhtarsk, although checkpoints blocking the western entrance into town remain under rebel control. It also said fighting was taking place in Snizhne, which lies directly south of the crash site, and in other towns in the east.
Meanwhile rebels in Donetsk said on Twitter that fighting took place in the village of Rozsypne, where some of the wreckage still lays strewn and uncollected.
A rebel military leader, Igor Ivanov, told Russian state news agency RIA-Novosti that the village had fallen into government hands, but that information could not immediately be confirmed.
And in a possible indication of sagging morale within the rebels' ranks, the deputy leader of the rebels in Donetsk announced Monday that his immediate superior, Alexander Borodai, had left for Russia. Viktor Antyufeyev, who is a Russian national like Borodai, said he will take over as the separatist government's acting prime minister.
The rising loss of life was underlined by a report released Monday by the United Nations.
The U.N. High Commissioner for Human Rights said that at least 1,129 people have been killed between mid-April, when fighting began, and July 26. The report said at least 3,442 people had been wounded and more than 100,000 people had left their homes. A U.N. report from mid-June put the death toll at 356.
Navi Pillay, the U.N.'s top human rights official, also called for a quick investigation into the downing of the plane, which she said may be a war crime.
The U.N. said rebel groups continue to "abduct, detain, torture and execute people kept as hostages in order to intimidate" the population in the east. It said rule of law had collapsed in the rebel-held areas and that 812 people had been abducted in the Donetsk and Luhansk regions since mid-April.
It also reported heavy damage to electrical, water and sewage plants and cited the government estimate cost of rebuilding, $750 million, money the government would have to find by cutting social programs.
In their campaign to wrest control over more territory from separatist forces, Ukraine's army has deployed a growing amount of heavy weaponry. Rebels have also been able to secure large quantities of powerful weapons, much of which the United States and Ukraine maintain is being supplied by Russia.
The U.S. also says that Russia has been firing into Ukraine, and released satellite images Sunday that it says back up its claims that rockets have been fired from Russia into eastern Ukraine and heavy artillery for separatists has also crossed the border.
Russia's Defense Ministry spokesman Igor Konashenkov on Monday dismissed the images as fake. He said in a statement carried by the Russian news agencies that the satellite images released by the U.S. State Department can't serve as a proof because they lack precise locations and their resolution is too low.
With allegations that Russia is supplying weapons to the rebels and allowing Russian fighters to cross into Ukraine, the Organization for Security and Cooperation in Europe said it plans to begin deploying a border-observation mission on the Russian side on Tuesday. The mission is to be deployed at two checkpoints. It is unclear if they will be able to assess whether the border is being crossed at areas without checkpoints.
Leonard reported from Kiev, Ukraine. Associated Press writers Nataliya Vasilyeva and Vladimir Isachenkov in Moscow, David McHugh in Kiev, Ukraine, and John Heilprin in Geneva contributed to this report.