The United Nations on Monday flew its blue and white flag at half-mast at the UN Headquarters in New York to mourn the deaths of Polish President Lech Kaczynski and 87 other members of a Polish delegation who were killed in a plane crash on Saturday morning.

The UN flag is hoisted at half-mast to mourn the deaths of Polish President Lech Kaczynski and 87 other members of a Polish delegation who were killed in a plane crash on Saturday morning, at the UN Headquarters in New York, the United States, April 12, 2010. [Shen Hong/Xinhua]

?The UN flag was hoisted at half-mast before the UN Secretariat Building in the compound on the First Avenue in midtown Manhattan, central New York City.

"The United Nations stands with the Polish people and government at this time of sorrow and I hope they will be able to overcome this moment of sorrow," UN Secretary-general Ban Ki-moon told reporters here at a press conference prior to his departure to attend the summit on nuclear non-proliferation in Washington, D. C..

"The flag has been at half-mast," Ban said.

"I expressed my most profound condolence at such a tragic passing away of President Lech Kaczynski with whom I had been working very closely, particularly on climate change," he said.

The UN flag is hoisted at half-mast to mourn the deaths of Polish President Lech Kaczynski and 87 other members of a Polish delegation who were killed in a plane crash on Saturday morning, at the UN Headquarters in New York, the United States, April 12, 2010. [Shen Hong/Xinhua]

Conveying his heartfelt condolences at the tragic event, Ban said it must be a "very troubling, sad moment" for the Polish people.

"I wanted to speak with leadership of the Polish government at this time, but I have not been able to convey my personal condolences in person, but I am sure that I will have an opportunity of meeting a representative of Poland, the foreign minister, who will be in (Washington, D.C.)," he said.

Ban also said that he would discuss with the president of the UN General Assembly, Ali Treki, regarding a moment of silence to express condolences from member states.

On Saturday morning, a Polish government plane carrying a delegation for the 70th anniversary of the Katyn crime crashed at Smolensk, Russia, 18 kilometers from Katyn where WWII Polish officers were murdered 70 years ago.

All 97 passengers aboard the plane were killed, including President Kaczynski and his wife Maria.