KIEV: Four Ukrainian soldiers and two civilians were reported killed Friday in an upsurge in mortar and rocket attacks launched just days ahead of planned international talks on the crisis.

Local authorities in the rebel stronghold of Donetsk said two civilians were killed and seven injured in clashes around the industrial city’s disputed airport.

The air hub — once the busiest and most modern in the largely Russian-speaking east of Ukraine — has been held by a skeleton force of government soldiers since late May.

Almost daily attacks by pro-Russian insurgents on the airport have resulted in heavy civilian casualties caused by heavy rocket fire from both sides going astray.

The Ukrainian military said four of its soldiers had also been wounded in the past day of violence around the separatist province.

The press office for military operations in eastern Ukraine said army outposts were targeted 50 times by small arms fire, mortars and rockets over the last day.

Intensification in hostilities comes one month after a renewed truce led to a marked lull in the fighting that broke out in the spring.

Ukranian military spokesman Andriy Lysenko blamed the spike in rebel attacks on new supplies of weapons that he alleged they were provided by Russia under the guise of humanitarian aid.

Russia on Thursday sent its 11th shipment of trucks into eastern Ukraine that Moscow insisted were carrying winter supplies for civilians in the militia-controlled regions of Donetsk and Lugansk.

All the deliveries have been made without Kiev’s agreement and have been never fully inspected by international monitors stationed on site.