The arrest of the alleged spies raises fresh questions about Chinese involvement in Russia's invasion of Ukraine and Beijing's purported neutrality in the conflict. The Security Service of Ukraine (SBU) said its counterintelligence team had caught the alleged spies "red-handed" during the transfer of secret documents from a Ukrainian citizen.

Ukraine said on Wednesday it had detained a Chinese father and son, both suspected of spying on its prized Neptune anti-ship missile programme, a key part of Kyiv's growing domestic arms industry critical to its defence against Russian invaders.