French President François Hollande offered "all my solidarity" with relatives of the crash victims, and made calls for a wide-ranging investigation to determine what happened to the plane that was en route from Amsterdam to Kuala Lumpur.
Hollande, who is currently ona trip to Africa, said in a statement: "I learned with great emotion that airliner company "Malaysia Airlines"... crashed on Ukrainian soil."
"France demands that everything is implemented, to shed light on the circumstances that caused this tragedy," he added. "I express my solidarity with the relatives of the passengers."
Initial reports claimed there were at least four French nationals on board but that has not been confirmed.
Hollande's calls for an inquiry echoed by other world leaders.
For its part Britain has called for an UN-led investigation and is seeking an emergency meeting of the UN Security Council to discuss the crisis in Ukraine's rebel-held east -- which NATO described as "more and more dangerous".
"We believe that there must be a UN-led, international investigation of the facts," Foreign Secretary Philip Hammond told a press conference on Thursday.
US officials believe the plane was shot down by a surface-to-air missile, while comments attributed to a pro-Russia rebel chief suggested his men may have downed Malaysia Airlines flight MH17 by mistake, believing it was a Ukrainian army transport plane.
"The facts of what happened and who was responsible must be quickly established," the presidents of the European Council and Commission, Manuel Barroso and Herman Van Rompuy, said in a joint statement. "The inquiry must be rapid and complete."
UN chief Ban Ki-Moon echoed calls for a "full, transparent and international investigation".
'Shooting down of plane will not be a game changer'
Despite the fact most seem to believe the plane was shot down by Russian separatists, some analysts believe France and the rest of the EU, are unlikely to toughen their stance towards Vladimir Putin.
Philippe Migault, an expert on Ukraine from the Institute of International and Strategic Relations (IRIS) in Paris says there are too simply many economic interests at stake for Europe.
“France like other European countries will condemn the incident and demand an inquiry as well as an end to fighting in the region, but they won’t go much further,” Migault told The Local. “I don’t think we will see any major change.”
“There are just too many interests at stake. The Economic interests between the EU and Russia are just too great. We have seen the USA increase sanctions against Russia, but they have less at stake economically than countries like France and Germany.”
France has risked the wrath of the United States for its decision to continue to push through a multi-billion euro deal to sell two Mistral warships to Moscow.
France’s Foreign Minister Laurent Fabius has suggested he would look again at the deal in October, depending on the state of the crisis in Ukraine, but IRIS’s Migault says France are unlikely to pull the deal.
“The problem is half of the money has already been paid. If France pulled out it would have to reimburse the Russians and that would cost billions,” he said.
Airlines told not to fly over Ukraine
In France, a statement by junior transport minister Frederic Cuvillier said he told "French airlines to avoid Ukraine's air space as long as the reasons behind this catastrophe are not known."
Leading airlines quickly announced plans to route planes away from the area.
Air France said it had "taken the decision to no longer fly over eastern Ukraine as soon as it heard of the event."
A spokeswoman for German flag carrier Lufthansa told AFP it has decided to immediately make a "wide detour" around the area, and added: "Our passenger's safety is our top priority.
She noted however: "There was not and there is not at present an order to avoid flights in Ukrainian airspace."
In London, a spokesman for the British Department for Transport told AFP: "Flights already airborne are being routed around the area by air traffic control in the region."