By Matt Siegel
SYDNEY (Reuters) - Australia held a national day of mourning on Thursday for its citizens killed in the downing of Malaysia Airlines Flight MH17 in Ukraine last month, even as Russia said it was ratcheting up its response to Western sanctions imposed over the disaster.
Flags will fly at half mast to mark the tragedy, which claimed 28 citizens in Australia's worst overseas loss of life since a 2002 bombing on the Indonesian island of Bali that killed 88 Australians.
"Today the Australian nation expresses its gratitude for the lives so cruelly cut short and we express our solidarity with those who love them," Prime Minister Tony Abbott told an interfaith service at Melbourne's historic St. Patrick's Cathedral.
A total of 298 passengers and crew were killed in the MH17 crash, mostly Dutch, Australian and Malaysian citizens.
Many Western leaders believe the Boeing 777 was brought down by a Russian-supplied SA-11 missile deployed by pro-Kremlin separatists in eastern Ukraine, a charge both Moscow and the rebels deny.
Allegations that Russia was involved in the disaster have sparked widespread anger in Australia, which is due to host Russian President Vladimir Putin and other world leaders at a G20 summit in November.
Russia will ban all imports of food from the United States and all fruit and vegetables from Europe, the state news agency reported on Wednesday, in response to Western sanctions imposed over its support for the rebels.
But the crash has proven a boon for Abbott, whose tough stance on the tragedy has boosted his popularity after several political stumbles since his conservative coalition government took office late last year. [ID:nL4N0Q35JH]
(Reporting by Matt Siegel; Editing by Clarence Fernandez)