"We regret Russia blocked expanding mandate of #OSCE Obs.Mission at 2Rus.BCP's 2all border sections, adjacent2uncontrolled part of #Donbas," Ukraine's Mission to the OSCE tweeted on Thursday.
"Unwillingness to let int.observers in proves to Russia's interest in maintaining ways of reinforcement of its proxies in #Donbas," the Ukrainian mission added.
The OSCE in turn reported that the mandate of the OSCE Observer Mission at Gukovo and Donetsk would be extended until April 30 without changes.
"The OSCE's 57 participating States today took a consensus decision to extend the mandate of the OSCE Observer Mission at the Russian checkpoints Gukovo and Donetsk by three months to April 30, 2016. Under today’s decision the mandate of the Mission remains unchanged," the OSCE said in an official statement on Thursday.
Political Director at Ukraine's Ministry of Foreign Affairs Oleksii Makeiev commented on Russia's decision in Twitter: "Russia is doing its best to resists [Ukraine's retaking] control over the Ukrainian-Russian border. As it will halt the smuggling of Russian weapons and mercenaries."
As UNIAN reported earlier, Russia has repeatedly blocked the expansion of the mandate of the OSCE Observer Mission to all the checkpoints in occupied Donbas at the state border with Russia.