Kiev said Tuesday it detained a priest,  who used missions to Ukraine's conflict-ridden east to traffic arms including a grenade launcher and hand grenades.

The priest was detained several months ago in northwestern Ukraine, but his detention only public today on Tuesday after further police investigations, the Ukraine security services (SBU) said. "It is a very delicate topic", Olena Gitlyanska SBU spokeswoman told AFP.

Beginning in 2015, the cleric carried out repeated "preaching missions" to eastern Ukraine, investigators said, where government forces have been fighting separatists backed by Russia. "He returned with dangerous trophies, which he sold to friends," the SBU said in a statement.

Officials said there were recorded several instances of the priest selling weaponry, including a rocket-propelled grenade launcher, seven grenades and 800 grams of dynamite. The unnamed man, who was reportedly previous convicted of arms trafficking, now faces up to seven years in prison.

The case highlights the problem of illegal weapon trafficking which has escalated since 2014 when fighting broke out between the Ukraine government and separatists in the eastern Donetsk and Lugansk regions. Russia annexed the Crimean peninsula from Ukraine in 2014, a move which was met with harsh economic sanctions by Western countries. More than 13,000 people have been killed in fighting since.