The Palestinians have raised their flag at the United Nations for the first time, a symbolic gesture approved by a General Assembly vote at the world body earlier this month.

The red, black, white and green Palestinian flag was erected in the rose garden of the UN headquarters.

"In this historical moment, I say to my people everywhere: raise the flag of Palestinians very high because it is the symbol of our identity," Palestinian president Mahmud Abbas told a huge crowd.

"It is a proud day."

Ominous dark clouds gathered in the sky, threatening to mar with rain an occasion condemned by Israel and the United States as a gesture that would not serve the cause of peace.

The General Assembly voted September 10 to allow the flags of Palestine and the Vatican - both have observer status - to be raised at the world body alongside those of member states.

The resolution was backed by 119 countries, with 45 abstentions and eight votes against, including Australia, Israel and the United States.