Scores of mastic orchards on the Greek island of Chios were destroyed in a forest fire that has been ablaze for three days,, according to local officials on Monday.

The trees, whose aromatic resin is used in pastries as well as medicine and cosmetics, were damaged mainly by "the thick cloud of ash that covered the region", a fire department official told AFP.

The resin, derived from the Mediterranean shrub Pistacia lentiscus, had been almost ready for harvest when the wildfire hit.

Fanned by strong winds that reached 62 to 74 kilometres (38 to 46 miles) per hour on Sunday and Monday, the fire destroyed mastic crops in some 20 villages in the south of the island, before spreading to the north.

Firefighters continued to fight the blaze Monday with the help of seven helicopters.

According to estimates by local authorities, 30 percent of mastic resin output was destroyed.

The economy of the eastern island "depends on mastic cultivation, which suffered a major blow following this fire," Efthimis Moniaros, president of the Chios mastic growers association, told Skai radio.

Greek media reported that more than 5,000 hectares (12,355 acres) of pine forest and crops have gone up in smoke in the fire, with scores of hives also destroyed.

Several fires broke out over the weekend, with the most serious on the islands of Zante and Andros, on Mount Pelion and in the Peloponnese. Two French tourists were detained Monday on Andros on suspicion of starting the local fire, police said.

Greece is hit by wildfires, many started by arsonists, every summer, the flames fanned by high temperatures and strong winds.