Two Russian cosmonauts have exited the International Space Station for a spacewalk to install equipment and perform maintenance.

Video broadcast from Russian mission control outside Moscow showed Fyodor Yurchikhin and Oleg Skripochka carefully making their way out of a hatch Monday for a spacewalk expected to take about six hours.

Their main task is to install a workstation on the space lab's Zvezda service module for use by Russian and European space flyers.

Four of the station's crew remain inside: Russian Alexander Kaleri and American astronauts Douglas Wheelock, Shannon Walker and Scott Kelly.