Camouflaged rebel Alexander hung a sign on the wall of a busy supermarket Friday laying down the harsh new laws now governing the town of Novoazovsk after fighting drove out Ukrainian forces.

"Robbers, thieves and violent criminals must be judged before a military tribunal!" the decree read.

"Brothers and sisters, if you know of any act of pillaging, thievery or violence call 0102."

Some 12 kilometers from the Russian border, this once quiet seaside town is now firmly under separatist control after fighters flooded across from Russia this week opening up a new front in Ukraine's five-month insurgency.

While rebel leaders insist their volunteer forces conducted the offensive, Kiev and the West say the combatants who took Novoazovsk on Wednesday were Russian army troops.

"The liberation army of Novorossiya (New Russia) welcomes you," read another poster Alexander, who said he was a volunteer from Russia, was hanging up.

The name is a loaded Tsarist-era term for Moscow's former imperial holdings in east Ukraine that the rebels, and President Vladimir Putin, now use to refer to themselves.

"We came here to stay long. Do not believe the rumors that we are leaving. Our goal is to advance," the sign reads.

Outside in the streets, rebels patrol the town in a khaki pick-up truck with their red and blue flag flying off the back.

The symbol is also freshly painted on tanks positioned at the entrance to the town, their cannons pointing west towards government-held towns further down the coast.