ATHENS, Greece - A World War II bomb was defused Thursday near a landmark new park worksite on the coast of Greek capital Athens, with a local official warning more could be found.

The operation at the site of Hellinikon, 15 kilometres (nine miles) south of Athens, shut down one of the capital's busiest highways for around two hours and prompted the evacuation of four blocks of flats, officials said.

Giorgos Papanikolaou, mayor of the local suburb of Glyfada, told reporters at the scene that the 500-pound bomb (227 kilograms) had been successfully defused.

But he warned: "From what we are told, there may be others."

Hellinikon was bombed by Allied warplanes to prevent construction of an airstrip during Greece's occupation by Nazi Germany in World War II.

It later became Athens' official airport, until it was shut down in 2001.

The 200-hectare site is now being turned into what government officials say will become one of Europe's largest metropolitan parks.

The eight-billion-euro ($8.4 billion) private project is backed by a development fund operated by the wealthy shipowning Latsis family.

The initiative includes a residential skyscraper, hotels, a casino, marinas, a shopping centre and cultural venues.

Most of the project is to be completed by 2026.