Archaeologists have uncovered carved stucco panels depicting cosmic monsters, gods and serpents in Guatemala's northern jungle that are the oldest known depictions of a famous Mayan creation myth.

The newly-discovered panels, both almsot eight metres long and stacked on top of each other, were created around 300 BC and show scenes from the core Mayan mythology, the Popol Vuh.

It took investigators three months to uncover the carvings while excavating El Mirador, the biggest ancient Mayan city in the world, the site's head researcher, Richard Hansen, said on Wednesday.

The Maya built soaring temples and elaborate palaces in Central America and southern Mexico, dominating the region for some 2,000 years, before mysteriously abandoning their cities around AD 900.

The El Mirador basin was deserted much earlier, with the large urban population leaving a complex network of roads and waterways and a massive pyramid now covered under thick vegetation.

The earliest written version of the Popol Vuh was discovered in the early 1700s by a Spanish colonial priest, and the panels are the first known sculptural depictions of the main characters in the myth - two hero twins, Mr Hansen said.

"This is pre-Christian, it has tremendous antiquity and shows again the remarkable resilience of an ideology that's existed for thousands of years," Mr Hansen, an Idaho State University archaeologist who has worked at El Mirador for over a decade, said.

On one panel, the twins are depicted surrounded by cosmic monsters and above them is a bird deity with outstretched wings. On the other, there is a Mayan corn god framed by an undulating serpent, said Mr Hansen who worked as a consultant for Mel Gibson's 2006 movie about the Maya, Apocalypto.

Spread over more than 2,000 square kilometres, El Mirador is three times the size of Guatemala's famous Tikal ruins, a popular tourist destination. But El Mirador's conservation is threatened by drug traffickers who use the area to ship cocaine and heroin across the porous border with Mexico, deforestation by locals, looters who steal ancient artifacts to sell on the black market and wild animal poachers.

Last year, President Alvaro Colom announced the creation of a massive park in the dense jungle of northern Guatemala's Peten region, which would encompass both El Mirador and the already excavated Tikal.

The plan includes the construction by 2020 of a silent, propane-powered train to carry thousands of tourists to the ruins, currently only accessible by helicopter or a two-day hike through the jungle.