Russian president Vladimir Putin has begun moving troops from Syria to Ukraine to help in the Battle for Donbas, the Syrian Observatory for Human Rights (SOHR) claimed.

Military forces are being moved from Syria where the Kremlin had thousands of troops based since 2015, when Vladimir Putin ordered his fighters to support president Bashar al-Assad.

The Moscow Times reported that these troops are being stationed at three airports in Ukraine before being transferred to the frontline to increase Russia’s presence as fighting in the southeast increases.

“More than 63,000 Russian military personnel have deployed to Syria between 2015 and 2018, Moscow says, however it is unclear how many officers are currently stationed there. According to western intelligence, Russian forces have become frustrated with the resilience of Ukraine’s troops, which had drawn out the “special military operation” and has caused the Kremlin to change its plans from seizing Kyiv to gaining control of the Donbas,” the observatory wrote.

Russia’s abandoned air bases in Syria are being transferred to the Iranian military-political organisation, Islamic Revolutionary Guard Corps and the militant group Hezbollah, according to SOHR, citing sources.

The news comes as Ukraine has launched a series of counter-attacks in Kharkiv pushing Russian troops northward and Finland has made its intentions clear to apply for NATO membership.

Russia said that Finland’s move to join NATO would make Europe less stable and Moscow would be forced to take “retaliatory steps”. The Kremlin’s foreign ministry said Helsinki’s application, announced earlier in the day, is a “radical change” in the country’s foreign policy.

“Russia will be forced to take retaliatory steps, both of a military-technical and other nature, in order to stop threats to its national security arising,” the foreign ministry said. Meanwhile, Kremlin spokesman Dmitry Peskov said Finland’s Nato bid was a cause for regret.

He added that Finland had taken “unfriendly steps” against Russia. On possible responses, Peskov added: “Everything will depend on how this expansion process of Nato expansion plays out, the extent to which military infrastructure moves closer to our borders.”