Russian news agencies say that Alexander Vinnik, a Russian cryptocurrency expert who faced Bitcoin fraud charges in the United States, has returned to Russia after being freed in a swap that saw Moscow’s release of American Marc Fogel.

The United States has imposed a new round of financial penalties on people and entities involved in Russia’s financial sector.

Google Maps(CNN) - Rescuers on Sunday mounted a desperate search for survivors after a dam at a Siberian gold mine collapsed on Saturday, killing at least 15 people. Six people remained unaccounted after the dam collapsed near a settlement on the Seiba River in the region of Kransnoyarsk, approximately 2,500 miles east of Moscow, the Russian Emergencies Ministry for the Krasnoyarsk Region said. The ministry released images of first responders arriving in the remote region of Shchetinkino by helicopter to conduct search and rescue operations. According to the Emergencies Ministry, 174 people lived in the settlement. Krasnoyarsk Governor Alexander Uss said lax construction standards and weather conditions were among the possible causes of the dam break, Russian state news agency RIA-Novosti reported.

iStock/BWBImages(CNN) - Authorities in northern Russia detected a brief rise in radiation levels following a deadly explosion at a military training ground in the Arkhangelsk region, state news agency TASS reported Thursday. "The brief rise of the radiation level was registered in Severodvinsk at about noon," said Kseniya Yudina, a spokeswoman for the city, TASS reported. The Arkhangelsk regional governor told TASS that the area around the explosion would not be evacuated. State news agency RIA-Novosti, citing regional law enforcement, put the casualty toll higher, saying two people died and 15 were injured in the explosion. The agency told RIA-Novosti the incident occurred 30 kilometers from the city of Severodvinsk, and that circumstances were being clarified.