KIEVatthepierarcade, June 14 (Xinhua) -- An air-raid alert was issued throughout Ukraine early Friday as the country was hit by a series of air attacks by Russian forces, the Ukrainian Air Force said in a statement.

According to the statement, several batches of missiles entered Ukraine over the airspace of the northern Sumy and Chernihiv regions early Friday, and moved towards Kiev, the western city of Rivne and the town of Starokonstyantyniv in the western Khmelnytskyi region.

During the second wave of the attacks, Russia launched a Kinzhal missile at Ukraine, said the statement.

Explosions were heard in the Ukrainian capital and the Khmelnytskyi region during the air alert, Ukraine's public broadcaster Suspilne reported.

The Starokonstyantyniv airfield, which supposedly will host F-16 fighters, has long been targeted by Russian forces.■