Archaeologists have discovered a Viking ship burial in Norway using ground-penetrating radar that suggests the 20-metre keel and many of its timbers remain well preserved just half a metre below the topsoil.

The ship lies in farmland in Østfold county in south-east Norway. Just three other intact ship burials have been recorded in the country; the survival of this one is remarkable because the imposing burial mound that once covered it has long since been ploughed out. Another mound, Jelle mound, still rises high in the field, and the research has also traced the outlines of at least eight other previously unknown burial mounds that once surrounded it, and five nearby longhouses.

Project leader Lars Gustavsen, an archaeologist from the Norwegian Institute for Cultural Heritage Research (Niku), said: “The ship burial does not exist in isolation, but forms part of a cemetery which is clearly designed to display power and influence.”

There are no immediate plans for excavation, but further non-invasive research will map the remains and assess their condition.

The find was described as “incredibly exciting” by Knut Paasche, an expert on Viking ships at Niku. The researchers worked with motorised high-resolution ground-penetrating radar developed by the Ludwig Boltzmann Institute for Archaeological Prospection and Virtual Archaeology in Austria.

The ship burial forms part of a larger mound cemetery and settlement site next to the monumental Jelle mound. Photograph: Lars Gustavsen/NIKU

“This new ship will certainly be of great historical significance as it can be investigated with all modern means of archaeology,” Paasche said.

Viking ships, in which they raided, traded and struck terror across northern Europe, were precious objects, and such burials were reserved for high-status individuals. Others have been excavated to reveal warrior leaders with their weapons and other possessions heaped around them.

The first to be scientifically excavated in the UK was found in 2011 at Ardnamurchan, Scotland, the most westerly point of the mainland. It was a five-metre boat, surviving only as lines of hundreds of rivets and fragments of timber in the soil, that held a man buried with his shield, sword and spear and other grave goods including an Irish brooch and a drinking horn.