Just days after Russia reportedly transferred sophisticated anti-air missile systems to pro-Russian separatist fighters in Ukraine, Kiev reported on Sunday that a militants shot down another Ukrainian fighter jet.

“Ukraine’s military told AFP its MiG-29 warplane was blown out of the sky as it carried out ‘an assignment to eliminate a large group of terrorists’ in the strife-torn Lugansk region,” an AFP report read. Coming exactly one month after the downing of Malaysia Airlines Flight 17, this would be one of several military aircraft taken out of the sky by Russian rebels.

Meanwhile, Ukrainian forces appear to be enjoying some successes in their efforts to dislodge separatist fighters from their strongholds in the east. Ukrainian’s armed forces reportedly took control of a key police station in a residential area of the rebel-held city of Luhansk on Sunday, despite a recent influx of military equipment which local commanders allege is coming from Russia.

Similarly, separatist forces in the rebel-held city of Donetsk are also suffering setbacks. On Sunday, Kiev asserted that Yasynuvata, a town in the Donetsk region, fell to government forces.

With pro-Russian separatists in Ukraine’s east apparently losing ground, a convoy of vehicles which Russia claims is transferring humanitarian aid arrived on Sunday at the rebel-held border. The convoy has not crossed the border, however, reportedly because they lack security guarantees.

“The Red Cross, quoted by Reuters news agency, said Ukrainian and Russian customs officials had agreed to inspect the lorries,” the BBC reported. “But the Izvaryne crossing where the vehicles have arrived is controlled by rebels, so it is not clear how Ukrainian officials will reach them.”

The convoy has been parked near Ukraine’s border since Thursday, but Russia has apparently been reluctant to let the convoy proceed into Ukraine. “The Red Cross told AFP its officials had arrived at an area where some 300 Russian trucks are waiting but that official inspections of the cargo were yet to begin,” a Sunday report read.

Russian officials continue to contend that there are no plans to allow this convoy to cross the border until security considerations have been met. The forward positioning of the convoy could suggest that Russia is considering pressing ahead with its “humanitarian aid” mission, which would not be an unexpected development.

If the pro-Russian separatists continue to suffer the defeats they have been contending with at the hands of Ukrainian forces, Moscow’s hand may be forced. New equipment has been pouring in from Russia for weeks, but all the equipment in the world won’t matter if the separatist forces are dwindling.