Dutch investigators say cockpit recordings show no emergency in the moments before Malaysian Airlines Flight MH17 went down on July 17. Pro-Russian rebels fighting in eastern Ukraine are widely blamed for the incident.
The detention of the Russian paratroopers, who claim to have crossed the border accidentally, comes as the presidents of Russia and Ukraine attend a regional summit, with some speculating that the two may meet.
Russian trucks loaded with humanitarian supplies had been idling at the border, but some have now entered Ukraine without permission, which Kiev considers an act of aggression. Russian and Ukrainian leaders are to meet next week.
Islamic State militants had demanded millions of dollars for James Foley's release. While the US government refuses to pay ransoms to kidnappers, some European governments have done so in the past, enriching Al Qaeda and its affiliates.