Ukrainian forces are gearing up for warfare to reclaim the villages north of Novoazovsk coastal town as Pro-Russian rebels work to create a second front in eastern Ukraine.
Ukrainian President Petro O. Poroshenko, meantime, had ordered a mandatory conscription for the country's armed forces.
Mykhailo Koval, deputy head of the national security council, said the mandatory conscription, suspended last year, would restart this fall.
Col. Andriy Lysenko, spokesman for the Ukrainian National Security Council, said Novoazovsk, which borders Russia, "is being shelled from both Russia and from positions on Ukrainian territory."
Besieged volunteer units of "patriots" leading the defence of the area are barely holding on.
Leaders of the great western nations immediately pounced on Russian president Vladimir Putin, warning of greater and massive consequences and sanctions.
But despite the invasion, U.S. President Barack Obama played down on a potential military action against Russia. Instead, Russia will be punished through increased economic sanctions.
Oleg Odnorozhenko, deputy head of Azov, another volunteer Ukrainian battalion, said no amount of sanctions will rattle Mr Putin.
"The west is acting not rightly - to put it mildly - allowing Putin to increase the aggression," Odnorozhenko said. "No sanctions will force Putin to refrain from his new Soviet project."
Alexey, a commander of the Dnipro Battalion, told VICE News that even with the reinforcements, they can barely sustain the fight. "We need armament. We need anti-tanks artillery to hold the city."
Rebels had already captured seven villages north of Novoazovsk, a town with 12,700 people.
On Monday, a convoy of Russian vehicles of 10 tanks, two armored vehicles, and two trucks, entered the country, the Ukrainian government claimed.
As expected, Russia denied ever sending troops or artillery into eastern Ukraine. But just on Tuesday, 10 Russian paratrooper soldiers were captured by Ukrainian forces inside its borders. Moscow claimed the men were conducting a military exercise and had perhaps crossed the border by "accident."
However, NATO on Thursday released satellite images that allegedly showed Russian armoured vehicles and artillery had been crossing for at least a week into Ukraine. NATO estimated there are over 1,000 Russian soldiers fighting in Ukraine.
Incidentally, the advance of pro-Russia forces came just three days after Ukraine's Independence Day, where 145 military vehicles and 2,500 servicemen marched through the capital on Sunday.
VICE News gathered from volunteer battalions the enemy fighters were digging in artillery positions. And because they only have small arms and a few RPGs (rocket propelled grenade launchers), they are unable to hold Novoazovsk. "We can't fire back at the artillery so we keep getting pushed back."
Lysenko had admitted all the villages to the north had been lost.