"The scale and scope of Ahtisaaris activities are almost beyond belief," the head of the Nobel committee Ole Danbolt Mjoes said before he handed over the Nobel gold medal and diploma to the former Finnish president in Oslo.
Ahtisaari received his prize, which also includes the prize sum of 10 million Swedish kronor (1.2 million dollars, 950,000 euros), in an Oslo city hall bedecked with red flower decorations as the Norwegian royal family, politicians and celebrities looked on.
The veteran peace broker has over the past 30 years helped resolve conflicts in troublespots such as Indonesia, Namibia, Northern Ireland and the Balkans.
In his acceptance speech, Ahtisaari stressed the need to resolve one of the world’s most drawn-out conflicts, calling on US president-elect Obama to give priority to a comprehensive peace deal in the Middle East when he takes office.
"I hope that the new president of the United States, who will be sworn in next month, will give high priority to the Middle East conflict during his first year in office," the 71-year-old career diplomat said in an advance copy of his Nobel acceptance speech obtained by AFP.
He insisted that to make peace in the Middle East a wider perspective was needed.
In addition to the United States, the European Union, Russia and the United Nations also needed to be involved in reaching the accord, which he said should stretch "from Israel and Palestine to Iraq and Iran."
"If we want to achieve lasting results, we must look at the whole region," he said, stressing that "we cannot go on year after year simply pretending to do something to help the situation in the Middle East. We must also get results."
"All conflicts can be settled, and there are no excuses for allowing them to become eternal," he said.
In Europe, the Finn played a key role in bringing an end to hostilities in the breakaway Serbian province of Kosovo in 1999, before attempting in vain from 2005 to 2007 to broker an agreement between Belgrade and Pristina on the provinces status.
Kosovo, inhabited mainly by ethnic Albanians, unilaterally declared its independence from Serbia in February this year, to the great dismay of Belgrade and its allies in Moscow.
Ahtisaari said at a press conference in the Norwegian capital on Tuesday that he believed Kosovos independence was "irreversible".
As for the Middle East conflict, the peace broker stressed in his acceptance speech that "it is simply intolerable that violent conflicts defy resolution for decades causing immeasurable human suffering and preventing economic and social development".
He flatly rejected the idea that the drawn-out conflict between Israel and the Palestinians was rooted in religious rivalry.
"Religions themselves are ... peace-loving. They can also be a constructive force in peace-building, and this also applies to the Middle East."
Ahtisaari also addressed the global economic crisis, warning that it was worsening widespread inequality, which in turn breeds conflicts.
The international community needed now more than ever to focus on helping the worlds poor, who will be hardest hit by the turmoil, he said.
"The effects of this crisis may prove another major setback for the developing world," Ahtisaari said, pointing out that "the very poorest people are already being hit hardest by the impact of climate change, rising food prices and lower levels of foreign trade."
Later Wednesday, the winners of the Nobel prizes for medicine, physics, chemistry, literature and economics were to receive their awards at a formal ceremony in Stockholm, followed by a gala banquet for 1,300 invited guests.