Intense artillery fire has broken out in the pro-Russia separatist bastion of Donetsk in eastern Ukraine, according to AFP journalists in the area.

The shelling close to the town centre started at 2:00am local time (2300 GMT Saturday) and could still be heard, at the same intensity, two hours later.

It was a level of military activity not seen in the region since a barely-observed ceasefire was signed in September.

It was not immediately possible to evaluate the consequences of the artillery bombardment due to an overnight curfew imposed by the rebel authorities in Donetsk.

The Organisation for Security and Cooperation in Europe (OSCE) voiced concern on Saturday after its monitors witnessed columns of tanks, howitzers and troop carriers moving through east Ukraine in territory held by pro-Russia separatists.

The OSCE report came a day after Ukraine's military said it had spotted a large column of tanks and other heavy weapons entering the country from Russia across a section of border that has fallen under control of rebel fighters.

Ukraine's military said there was bloody fighting on Saturday around Donetsk international airport, where government forces are defending a pocket of territory near the biggest rebel-held city.

Russia has denied it backs the rebels in the east.

PHOTO CAPTION

Ukrainian servicemen fix an Armored Personnel Carrier at their position near Luhansk, Ukraine, 08 November 2014.

Aljazeera