One of Iceland's most feared volcanoes, Hekla, looks ready to erupt, with measurement instruments showing likely magma movement, an Icelandic geophysicist said.
The volcano is close to the ash-spewing Eyjafjoell, which last year caused the world's biggest airspace shut down since World War II, affecting more than 100,000 flights and eight million passengers.
The Iceland Civil Protection Authority said it was closely monitoring the situation.
"The movements around Hekla have been unusual in the last two to three days," University of Iceland expert Pall Einarsson said.
While this might not necessarily mean an immediate blast, "the volcano is ready to erupt," he stressed. "The mountain has been slowly expanding in the last few years because of magma buildup," he explained. The volcano, dubbed by Icelanders in the Middle Ages as the "Gateway to Hell," is one of Iceland's most active, having erupted some 20 times over the past millennium, most recently on February 26, 2000.