Greenpeace activists projected the slogan "No Trump, Yes Paris" onto a building in central Warsaw as US president Donald Trump visited Poland, in protest at the US withdrawal from the Paris climate agreement.
The action coincided with Mr Trump's arrival in Warsaw and Greenpeace said it did not include a gathering of protesters.
The authorities said they did not expect any major protests against Mr Trump on Thursday, though there were some small-scale demonstrations planned by a marginal opposition party.
Mr Trump announced in May that he would pull the United States from the Paris Climate Agreement, a global accord on fighting climate change. The move drew criticism from governments and climate change activists around the world.
Poland opposed European Union's climate policy to reduce carbon emissions but supported the Paris deal as it did not imposed specific obligations on signatories.
The White House has said Mr Trump will hold a speech underlining his commitment to the North Atlantic Treaty Organization. He will also meet with EU countries closest to Russia before heading to the G20 summit in Germany which begins on Friday.
Climate issues are not expected to be discussed during Trump's visit in Warsaw, but will be a key topic at the summit of the Group of 20 leading economies.
* Reuters
