A Malaysia Airlines aircraft, bound for Kuala Lumpur from Amsterdam, was shot down near Ukraine's border with Russia on Thursday, killing all 298 people on board.
U.S. intelligence officials have confirmed that a ground-to-air missile brought down the plane, although it's still not clear who fired it.
"With respect to the Malaysian Airlines' disaster today in Ukraine, I'm closely monitoring the reports. There is clearly a need for a full and transparent international investigation. For the moment, I offer my deep condolences to the families and loved ones of the victims and people of Malaysia."
Ukraine's intelligence agency has since released audio of a purported telephone conversation between pro-Russian separatists in the east of Ukraine.
They are heard talking about the downed jet, and seem confused about the presence of a passenger plane in the airspace above them.
The tape has not been independently verified, but it has added credence to suspicions that rebel forces are to blame.
"We do not exclude the possibility that this plane was also shot down and stress that Ukrainian Armed Forces did not perform any actions to fire at targets in the air."
"In this regard, I want to emphasize that this tragedy would not have happened if there were peace on that land, and in any case, if the military activities had not resumed in the southeast of Ukraine."
More than half of the passengers of Flight 17 were Dutch nationals.
The identities of 41 passengers have yet to be verified.
Shin Se-min, Arirang News.