This is stated in the OSCE SMM report.
"Beyond respective withdrawal lines but outside designated storage sites, near “LPR”-controlled Uspenka (23km south-west of Luhansk) the SMM saw three tanks (T-72) heading south," the report says.
In addition, the SMM observed weapons that could not be verified as withdrawn, as their storage did not comply with the criteria set out in the 16 October 2015 notification from the SMM to the signatories of the Package of Measures on effective monitoring and verification of the withdrawal of heavy weapons. “In areas not under government control beyond the respective withdrawal lines in Donetsk region, the SMM noted that 11 multiple launch rocket systems (BM-21 Grad, 122mm) were again missing. At another area, the SMM observed five self-propelled howitzers (2S1) and noted that two self-propelled howitzers (2S1) were again missing. The Mission was denied access to a heavy weapons holding area,” the report reads.