Alexander Borodai also said the bodies recovered from the crash site in eastern Ukraine would remain in refrigerated train cars at a station in the rebel-held town of Torez, 15 kilometers (9 miles) away, until the arrival of an international aviation delegation.
Ukraine and the separatists accuse each other of firing a surface-to-air missile Thursday at Malaysia Airlines Flight 17 as it flew from Amsterdam to Kuala Lumpur some 33,000 feet (10,000 meters) above the battlefields of eastern Ukraine. Both deny shooting down the plane. All those onboard the flight - 283 passengers and 15 crew - were killed.
It was immediately not clear Sunday if the rebels and the Ukrainian government were working together or were at odds with each other on recovering the bodies - and from their comments, many of officials didn't appear to know either.
A Ukrainian emergency spokeswoman said the armed rebels had forced emergency workers to hand over all 196 bodies recovered from the Malaysia Airlines crash site and did not tell them where the bodies were going. Ukrainian government officials, meanwhile, prepared a disaster crisis center in the government-held city of Kharkiv, expecting to receive the bodies, but those hopes appeared delayed or even dashed Sunday.
"The bodies will go nowhere until experts arrive," Borodai said, speaking in the rebel-held city of Donetsk.
Borodai said he was expecting a team of 12 Malaysian experts and that he was disappointed at how long they had taken to arrive. He insisted that rebels had not interfered with the crash investigation, despite reports to the contrary by international monitors and journalists at the crash site.
The rapid-fire developments Sunday morning came after a wave of international outrage over how the bodies of plane crash victims were being handled and amid fears that the armed rebels who control the territory where the plane came down could be tampering with the evidence.
Ukraine says Russia has been sending sophisticated arms to the rebels, a charge that Moscow denies.
The U.S. embassy in Kiev issued a strong statement Sunday pointing to Russian complicity in arming the rebels, saying it has concluded "that Flight MH17 was likely downed by a SA-11 surface-to-air missile from separatist-controlled territory in eastern Ukraine." It said over the weekend of July 12-13, "Russia sent a convoy of military equipment with up to 150 vehicles, including tanks armored personnel carriers artillery, and multiple rockets launchers" to the separatists. The statement also said Russia was training separatist fighters in southwest Russia, including on air defense systems.
The rebels have been strictly limiting the movements of international monitors and journalists at the crash site, which is near the Russian border, and Ukraine's Emergency Ministry said its workers were laboring under duress, overseen by the armed rebels.
Associated Press journalists saw reeking bodies baking in the summer heat Saturday, piled into body bags by the side of the road or still sprawled where they landed in the verdant farmland in eastern Ukraine after their plane was shot out of the sky.
By Sunday morning, AP journalists saw no bodies and no armed rebels at the crash site. Emergency workers were searching the sprawling fields only for body parts.
There was no immediate word on the bodies of the 102 other plane victims, but Michael Bociurkiw, a spokesman for monitors from the Organization for Security and Cooperation in Europe, said some bodies have likely been incinerated without a trace.
"We're looking at the field where the engines have come down. This was the area which was exposed to the most intense heat. We do not see any bodies here. It appears that some have been vaporized," he told reporters in Kiev on Sunday, speaking via phone from the crash site.
Alexander Pilyushny, an emergency worker combing the crash site for body parts Sunday, told the AP it took the rebels several hours Saturday to cart away the bodies. He said he and other workers had no choice but to hand them over.
"They are armed and we are not," Pilyushny said.
Nataliya Khuruzhaya, a duty officer at the train station in Torez, said emergency workers loaded plane victims' bodies Sunday into five sealed, refrigerated train cars.
Vasily Khoma, deputy of governor of the Kharkiv region where Ukraine has set up a crisis center to handle the disaster, said the Ukrainian state railway company had provided the refrigerated train cars. Kharkiv is 300 kilometers (185 miles) north of the crash site.
He said no information was available on when airplane parts would be brought to the city and that the priority now was on recovering bodies. He said a mobile lab to handle DNA analysis was being delivered from Dnipropetrovsk.
Residents in Kharkov have been inundating a special call center to offer their services as volunteers. Ten hotels in Kharkiv say they will give free rooms for relatives of the victims.
In a blistering article for the Sunday Times, British Prime Minister David Cameron called the attack a "direct result of Russia destabilizing a sovereign state, violating its territorial integrity, backing thuggish militias and training and arming them."
"We must turn this moment of outrage into a moment of action," he wrote.
In a coded rebuke of German Chancellor Angela Merkel and other European leaders who have blocked efforts to impose tougher sanctions on Russian President Vladimir Putin for Russia's actions in Ukraine, Cameron said Europe must now "respond robustly."
"For too long, there has been a reluctance on the part of too many European countries to face up to the implications of what is happening in eastern Ukraine," Cameron wrote.
Dutch Foreign Minister Frans Timmermans, speaking in Kiev, demanded that the culprits be found.
"Once we have the proof, we will not stop until the people are brought to justice," he said.