Israel has deported Swedish climate activist Greta Thunberg and 170 other pro-Palestinian activists who were detained last week while trying to breach Gaza's sea blockade to deliver aid.

Thunberg raised her hand as dozens of supporters gathered at the Athens airport to offer her flowers.

The Israeli Foreign Ministry said the activists were sent to Greece and Slovakia. They included citizens of Greece, Slovakia, France, Italy, the UK, and the US.

The activists have repeatedly denied "fake news" allegations that they were abused while in detention and denied their basic rights.

Of the 479 people who arrived on 42 boats, 341 have been deported, the ministry said.

The 138 activists are being held in Israel. More than 40 were confirmed to be on hunger strike on Sunday, according to a report by the Global Sea Flotilla (GSFF).

Its aim is to "break the illegal blockade of the Gaza Strip, open a humanitarian corridor, and stop the genocide against the Palestinian people," it said.

It’s said the detentions violated international maritime and humanitarian law.

Israeli authorities, for their part, said they had imposed a legal ban and that the boats were carrying only two tons of aid, so the case was "a matter of concern."