Ukraine’s counter intelligence chief claims to have “compelling evidence” that Russian citizens fired a missile that the Ukrainian authorities claim brought down Malaysia Airlines flight MH17.

Vitaly Nada told a news conference: “We have compelling evidence that this terrorist act was committed with the help of the Russian Federation. We know clearly that the crew of this system were Russian citizens.”

He also called on the Russian government to hand over the names of those involved in the alleged attack so that the Ukrainian authorities could question them.