Dozens of firefighters have been battling a blaze at Tokyo’s Tsukiji fishmarket, the world’s largest and one of the capital’s most popular tourist sites.

Grey smoke billowed over the city as the fire spread through five buildings covering around 300 square metres.

The fire broke out just before 5 p.m. and 44 fire trucks were on the scene. But efforts to contain the flames were hampered by the area’s narrow streets and tight-knit buildings.

The cause was not immediately known and there were no immediate reports of injuries or people trapped.

The 80-year-old Tsukiji fish market draws tens of thousands of visitors a year to its warren of stalls laden with exotic species of fish and fresh sushi, part of a tourism boom that is a key part of Prime Minister Shinzo Abe’s economic plan.

The fire was in Tsukiji’s “outer” market – an area packed with informal restaurants where tourists can tuck into fresh seafood plates and sushi.

The Tsukiji “inner” market, where most seafood wholesalers are located and tuna auctions are carried out at dawn, was not affected.

In June, Tokyo’s governor announced a long-delayed plan to move Tsukiji from its current site on some of the city’s most prime real estate to a man-made island with contaminated soil.

The outer market is not scheduled to move.

Tokyo governor Yuriko Koike said the market’s age and vulnerability to a big earthquake meant it had to be rebuilt.