KYIV, July 3 (Reuters) - Ukrainian authorities have charged a former top security official with treason, Kyiv's domestic intelligence agency said on Monday, in a case that highlights efforts to weed out Russian spies from within.

Oleh Kulinich, who headed the Security Service of Ukraine's (SBU) Crimea directorate, was arrested last July on accusations of recruiting other Russian-friendly operatives on orders from Moscow.

Investigators said Kulinich was working for Russia's Federal Security Service and was overseen by other former Ukrainian officials who had defected to Moscow, which launched a full-scale invasion of Ukraine in February 2022.

"This is a clear signal to all those who work for the enemy: the SBU will definitely find you and make you answer for what you have done," SBU chief Vasyl Malyuk, who oversaw the operation to detain Kulinich, said in a statement.

Kulinich could not be reached by Reuters for comment. If convicted, he faces up to 15 years in prison.

President Volodymyr Zelenskiy last year hailed Kulinich's arrest as part of a process of "self-purification".

Zelenskiy also sacked then SBU chief Ivan Bakanov and Ukraine's top prosecutor, citing dozens of cases of collaboration by members of their agencies.

Ukrainian authorities are also investigating Andriy Naumov, a former head of the SBU's department of internal security, who turned up in Serbia last year in a car stuffed with cash and emeralds, police said.