Advance a breakthrough for govt forces after four months of fighting

Ukrainian forces battled into a key rebel bastion as fresh claims that rocket launchers had crossed over from Russia stoked tensions on Sunday ahead of talks between Kiev and Moscow's top diplomats.

The foreign ministers of Russia, Ukraine, Germany and France gathered for a snap meeting in Berlin, after Western leaders had scrambled frantically to contain the crisis in Ukraine.

Kiev's military said it hoisted the national flag over a district police station in a northeast suburb of the second-largest rebel bastion of Lugansk after a fierce battle with separatists on Saturday.

A push into the city limits of the stricken 420,000-strong industrial hub would be a major breakthrough for government forces after four months of fighting that has claimed more than 2,100 lives and brought the region to the brink of a humanitarian catastrophe.

Ukraine also ramped up the stakes before the talks in Germany by alleging another military convoy, including three Grad rocket systems, crossed over from Russia.

The fresh claims come as a furor still swirls over Kiev's earlier boasts that it destroyed part of a Russian armored convoy that breached the frontier on Thursday.

Ukrainian Foreign Minister Pavlo Klimkin said Sunday's talks with his Russian counterpart, Sergei Lavrov, would "not be easy" as Germany also demanded that Moscow clarify rebel claims that they had received hundreds of fighters trained in Russia to bolster their insurgency.

"It is important to stop the flow of weapons and mercenaries from Russia," Klimkin wrote on Twitter.

Russia earlier dismissed claims that it had sent in hardware as "fantasies", and it again denied persistent allegations by the West that it is arming the rebels.

Aid checks to start?

Meanwhile, Russia and Ukraine appeared to edge closer to reaching a deal over a mammoth Russian aid convoy parked near the border as Ukrainian officials prepared to inspect the first of about 300 trucks.

An AFP journalist saw 16 trucks drive from a parking lot where they have been idling since Thursday to a Russian border post about 30 km away.

The West fear the convoy could be a "Trojan horse" to help the rebels in eastern Ukraine, or provide Moscow with an excuse to send in the 20,000 troops that NATO says it has massed on the border.

(China Daily 08/18/2014 page12)