"We can no longer stand this outrage, these open-faced lies and (Kiev's) refusal to reach an agreement. Russia has decided to act," the foreign ministry said in a statement.
"Our humanitarian aid column is starting to move in the direction of Lugansk."
An AFP photographer at the border said the first ten Russian trucks had crossed the frontier and reached a customs point inside Ukraine.
Several of the nearly 300 vehicles had been cleared by both countries' customs authorities yesterday and were waiting for the green light to enter Ukraine from an International Committee of the Red Cross (ICRC) team that is overseeing the operation.
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The ICRC meanwhile said it will not launch the aid delivery mission until it receives firm security assurances from both Kiev and the insurgents that the column will not be attacked.
The Russian foreign ministry appeared to suggest that Moscow has decided to act even without the Red Cross's permission.
"We of course are ready to have (the column) accompanied by the ICRC, and for its involvement in aid distribution," said the ministry.