Russia's President Vladimir Putin speaks during his meeting with Palestinian President Mahmoud Abbas at the Novo-Ogaryovo state residence outside Moscow June 25, 2014. The presidents of Russia, Germany, France and Ukraine held a joint phone call on Wednesday to discuss the situation in Ukraine, Kremlin spokesman Dmitry Peskov told reporters. REUTERS/Alexei Druzhinin/RIA Novosti/Kremlin

Russian President Vladimir Putin “expressed his profound condolences” to Malaysian Prime Minister Najib Razak Friday, the Kremlin said, on the loss of Malaysia Airlines Flight MH17, which was shot down over pro-Russian separatist-held territory in Ukraine.

Russia says both leaders agreed “it was important to ensure an objective international investigation into the disaster’s causes.” Putin also said he supported “an immediate end to the military operations in southeast Ukraine,” so a proper investigation can be conducted.

Western and Ukrainian leaders have accused Putin of aiding the separatists suspected of shooting down the aircraft since hostilities began earlier this year in Ukraine. He has denied the accusations.

Western leaders have expressed concern that the crash site may be tampered with before international investigators can reach it. The crash site lies in the heart of separatist-held territory in eastern Ukraine, where Ukrainian forces and the pro-Russian rebels have been fighting for months.

Reports say separatists have recovered MH17’s black box flight recorders, which are the most important pieces of equipment used to determine the cause of aviation accidents. Some separatists have claimed they will send the black boxes to Moscow for analysis, but Russian Foreign Minister Sergey Lavrov said Russia has “no plans to seize the flight recorders.”

Separatist leaders agreed to allow international experts from the Organization for Security and Cooperation in Europe to reach the crash site unhindered, but there have been reports of investigators being fired upon and kept out.