A planned spacewalk by two cosmonauts at the International Space Station (ISS) has been canceled due to technical problems. Before the exit hatch was opened, a warning signal went off for an initially unknown reason, the Russian space agency Roskosmos said on Thursday morning. The US agency Nasa spoke on Twitter of a coolant leak in the Russian Soyuz capsule - but at the same time gave the all-clear: "The spacecraft is in good condition and the Expedition 68 crew is safe."

The two Russians Sergei Prokopjew and Dmitri Petelin should have left the station in the early hours of the morning to work outside the ISS. Roskosmos announced an investigation into the incident.

Prokopyev and Petelin flew to the ISS in the Soyuz capsule in September together with NASA astronaut Frank Rubio. In addition to them, US astronaut Nicole Aunapu Mann, her colleague Josh Cassada, Japanese astronaut Koichi Wakata and cosmonaut Anna Kikina are currently on board the station around 400 kilometers above the earth.