By Friday afternoon, Stoltenberg was on his way to Madrid, CNN reported.
Earlier, Norwegian officials posted a photograph Friday of Stoltenberg sitting in what appears to be a VIP lounge gazing down at his iPad. The caption reads: "The prime minister is working at the airport."
Airports in Norway, like those in most of northern Europe, have been closed because of ash from a major volcanic eruption in Iceland.
Stoltenberg was in the United States to attend the nuclear summit in Washington and participate in a conference at the United Nations on maternal mortality. But he also took some time off to go shopping.
"It's very normal for a PM to travel abroad so this is not different from the other travels, it's just lasts some days more than expected," the stoic prime minister told CNN. "We have the Internet, the mobile phone. I also use an iPad, which is excellent."
Stoltenberg told CNN he had managed to get on a flight to Madrid and hoped to be home Saturday after a long drive across Europe.