The border service added that attacks are being carried out in Luhansk, Sumy, Kharkiv, Chernihiv and Zhytomyr regions
Ukraine has confirmed attack from Russia.
Ukraine said Russia attacked it through multiple borders.
According to the Ukrainian state border service, early Thursday morning, its state sovereignty was breached through its borders with Russia, its borders with Belarus and its borders with the Russian annexed Crimea.
"At about 5:00 a.m., the state border of Ukraine in the area with the Russian Federation and the Republic of Belarus was attacked by Russian troops supported by Belarus," the service said.
The border service added that attacks are being carried out in Luhansk, Sumy, Kharkiv, Chernihiv and Zhytomyr regions — areas on the eastern and northern borders of Ukraine. The attacks are targeting border units, border patrols and checkpoints using artillery, heavy equipment and small arms, the border service said.
"In addition, the attack takes place from the Autonomous Republic of Crimea side," said the service.
Ukraine is firing back: It added that border guards, along with Ukraine's Armed Forces and National Guard, are "firing at the enemy" depending on the situation on the border.
The Ukrainian air force also revealed that as at press time it had shut down five Russian planes and several attack helicopters