One of the passengers was spotted and rescued, the fate of the remaining 12 is unknown, the ministry said.
"A helicopter, which crashed into shallow waters near Zmeiny Island, has been located. One of the passengers was spotted and taken to hospital. Rescuers are searching for the others," Ihor Krol, head of the ministry's press service, said.
He said the accident occurred near the island at about 14:00 Moscow time (11 a.m. GMT). The helicopter had taken off from Odessa, Ukraine's largest port.
Crashes of Mi-8 Hip transport helicopters, first introduced to the Soviet Air Force in the late 1960s, are a relatively common occurrence in countries that use the aircraft. Three accidents involving the helicopter have occurred this year alone.
A Mi-8 crashed with 11 climbers on board in the former Soviet Central Asian republic of Tajikistan on March 8, killing one person and injuring five others. All 10 UN personnel on board a Mi-8 died, when the helicopter crashed in Nepal on March 3. And five people died in a Mi-8 crash in Kazakhstan in late February.
