Ukraine has launched what appears to be its first major assault against pro-Russian forces who have seized government buildings in the country's east, with fighting breaking out Friday around a city that has become the focus of the insurgency. Three deaths were reported in early fighting. Russian President Vladimir Putin's spokesman said the offensive "effectively destroyed the last hope for the implementation of the Geneva agreements" which were intended to defuse the crisis. Both sides said that two Ukrainian helicopters were shot down and their pilots were killed. The Ukrainian Security Service said one of the helicopters was shot down with a surface-to-air missile, which it said undercut Russia's claims that the city is under control of civilians who took up arms. A spokeswoman for the pro-Russian militants said one of their men was killed and another injured. She offered no further details.