Ukraine says it has started an “anti-terrorist” operation against pro-Russian militants in the east of the country.
Several helicopters and fighter jets have been seen over the town of Kramatorsk with sporadic gunfire heard from the military airfield.
Russian state news agencies report up to a dozen people have been killed but our correspondent there has seen no evidence of any deaths or injuries.
It comes a day after a Ukrainian ultimatum expired for the rebels to lay down their weapons.
The acting Ukraine President Oleksandr Turchynov earlier told parliament the operation would be carried out “stage by stage, in a responsible manner.”