Thousands of people opposed to Israel's participation in the Eurovision Song Contest demonstrated on Thursday ahead of this year's second semi-final.

More than 10,000 people, among them climate activist Greta Thunberg, gathered to take part in the rally, according to police estimates.

Just hours later, Israeli contestant Eden Golan performed her song "Hurricane," making the final following a public vote.

Metal barricades and large concrete blocks were put up around the Malmo Arena in the Swedish city hosting the competition, and local police received back up from Danish and Norwegian colleagues.

Though police said the march through the city was "quiet," demonstrators set off smoke flares in the colors of the Palestinian flag during a noisy rally where participants chanted the contentious slogan, "from the river to the sea, Palestine will be free" as well as "Israel is a terrorist state" calling for a cease-fire in Gaza.

Organizers of the protests say they plan to march again before the final on Saturday.

Earlier, the Israeli government issued a clear warning to its citizens citing "tangible concern" that they could be targeted, and loud booing could be heard as Eden Golan performed during dress rehersal.

The European Broadcasting Union (EBU), which organizes the pan-continental pop competition, ruled that Israel is allowed to compete, despite months of vocal opposition against the country's participation in the midst of the Israel-Hamas war.

Golan was forced to change the title and lyrics of her song before being allowed to compete, however. It had originally been titled, "October Rain," in what seemed to be a reference to the October 7 Hamas attack on Israel that sparked the current war.

The EBU claims Eurovision is apolitical but critics have highlighted Russia's exclusion from the competition over its 2022 invasion of Ukraine. Belarus was excluded a year earlier over its record on human rights and freedom of the press. This year's competition also bans the display of Palestinian flags.