A metal sphere that washed up on a beach in Japan, perplexing locals and setting off widespread speculation, has been removed, according to local media.Pictures showed a heavy lifting machine picking up the huge sphere.

Local officials in Hamamatsu said that it will be stored "for a certain period of time" then "disposed of". But many have also questioned why Japanese officials have not come out and clearly said what it is.

Interest in the object - dubbed "Godzilla egg", "mooring buoy" and "from outer space" - started earlier this week after a local alerted police upon noticing the unusual object on the shore.

Police, and even a bomb squad, were sent to check out the object.

Authorities cordoned off the area and conducted X-ray exams which did not reveal much more - other than confirming the object was safe.Now it has been removed.

"I think everyone in Hamamatsu City was worried and curious about what it was about, but I'm relieved that the work is over," a local official told Japanese media.

Many also questioned on social media why Japanese officials have not explained what it is. Others have voiced embarrassment at the whole episode.

"I can't believe officials from a country surrounded by ocean don't recognise a ball buoy," read one tweet.

"OMG! It's a steel mooring buoy people. I'm embarrassed to be Japanese," said another.

Hamamatsu's local civil engineering office said it "considers it to be a foreign-made buoy".

Prof Mark Inall, an oceanographer at the Scottish Association for Marine Science, said he knew what it was "instantly".

"It's very recognisable," he told the BBC. "We use (them) to keep instruments floating in the ocean."

They often wash up on the coast of Scotland, he added.

While Professor Inall said he was surprised that the metal sphere was not identified more quickly, he acknowledged that the general public wouldn't necessarily have known what it was.

"It could be confused for a World War 2 mine ... but those would have spikes sticking out of them," he said.

He added that the objects can float in the ocean for decades, and can lose their markings and get rusty when they wash ashore.

The buoys can break free from their anchorage either in a violent storm or from being pulled by a big fishing vessel, Professor Inall said.

The Japanese authorities' response to the metal sphere was as curious as the object itself.

The mysterious ball washed up amid a heightened sense of nervousness here. Last week Japanese media was discussing the ramifications of North Korea's recent missile activity.

On Saturday an intercontinental ballistic missile (ICBM) landed in Japan's territorial waters. On Monday, North Korea fired two ballistic missiles into the Sea of Japan after the United States held joint exercises with East Asian allies.

There's also the issue of China's spy balloons. On Wednesday, Japanese and Chinese officials held security meetings in Tokyo for the first time in four years, where Japan expressed concern about the surveillance balloons.

Last week the government here said at least three unidentified flying objects spotted over its territorial skies between 2019 and 2021 were "strongly suspected" to have been Chinese.

Beijing denied allegations of espionage and urged Tokyo to stop following Washington's lead in exaggerating Chinese threats.

Given this tense undercurrent of geopolitical events and perceived threats from its neighbours, the flurry of speculation in Japan is understandable.

"Given the recent events ... I could understand there's an interest in an unidentified floating object," Professor Inall said.