Kiev, Ukraine (CNN) -- Sporadic heavy artillery barrages and machine gun fire could be heard early Sunday on the outskirts of the southeastern Ukrainian city of Mariupol, raising questions about the viability of a ceasefire between the Ukrainian government and pro-Russian separatists. While the source of the weapons fire was not immediately clear, it came as the ceasefire appeared to be holding, a rare positive sign in a conflict that has ratcheted up tensions between Russia and the West. By late Saturday, however, bursts of heavy artillery and machine gun fire replaced the evident calm, a gas station was ablaze and cars carrying injured civilians could be seen on the roads.Sporadic heavy artillery barrages and machine gun fire heard near MariupolPoroshenko and Putin talk about ensuring truce lasts, Poroshenko's office saysRussia will respond if new EU sanctions are imposed, state media reportsEU nations agree on further sanctions against Russia, due to be adopted Monday
The last Russian aid convoy, which entered without _'s permission, was sent by road.