The leaders of the Group of Seven (G7) industrialized nations on Wednesday threatened more sanctions against Russia as they accused Moscow of continuing its destabilizing actions in eastern Ukraine.

The threat came one day after the United States and European Union unveiled sweeping sanctions targeting Russia's defense, energy and finance sectors to punish what they called its continued support for rebels in Ukraine's east in the aftermath of the shootdown there of Malaysia Airlines Flight 17 on July 17.

The leaders of Britain, Canada, France, Germany, Italy, Japan, the United States, plus the presidents of the European Council and the European Commission, voiced their "grave concern" about " Russia's continued actions to undermine Ukraine's sovereignty, territorial integrity and independence."

"We once again condemn Russia's illegal annexation of Crimea, and actions to de-stabilize eastern Ukraine," they said in a statement released by the White House. "Those actions are unacceptable and violate international law."

"Russia still has the opportunity to choose the path of de- escalation, which would lead to the removal of these sanctions," they added. "If it does not do so, however, we remain ready to further intensify the costs of its adverse actions."

The Russian Foreign Ministry on Wednesday slammed the Western sanctions as "destructive and short-sighted," warning they would " further complicate" Moscow-Washington ties and "create an unfavorable atmosphere for international affairs."

In their statement, the G7 leaders condemned the downing of MH17 which resulted in the deaths of all 298 aboard, and demanded "a prompt, full, unimpeded and transparent international investigation."

Heavy fighting between the rebels and government forces were still preventing international experts from reaching the MH17 crash site on Wednesday.

"We call upon all sides to establish, maintain and fully respect a cease-fire at and around the crash site, as demanded by UN Security Council resolution 2166, so that the investigators can take up their work and to recover the remains of all victims and their personal possessions," the G7 leaders said.

They urged Russia to end its support for rebels in eastern Ukraine and secure its border to stop the flow of weapons, equipment and militants, an allegation rejected by Moscow.