Updated

British Prime Minister David Cameron is demanding that Russia end its support for the rebels in Ukraine, arguing that Russia's policies destabilized the country and created the conditions that appear to have led to the downing of Malaysian Airways flight MH17.

In an unusual front-page op-ed in the Sunday Times, Cameron says there is growing evidence that separatist rebels, backed by Russia, shot down the aircraft, killing 298 people.

Cameron says that "if this is the case then we must be clear what it means: this is a direct result of Russia destabilizing a sovereign state, violating its territorial integrity, backing thuggish militias and training and arming them."

Cameron also took European leaders to task for vacillating on Ukraine. Some countries have pushed for tough action, but others have dithered.