Chinese dissident Liu Xiaobo has been awarded the Nobel Peace Prize in his absence at a ceremony in Oslo.
The prize was placed on an empty seat, as Liu is imprisoned in a cell in his home country.
It is the first time that a laureate under detention has not been formally represented since Nazi Germany barred pacifist Carl von Ossetzky from attending in 1935.
Liu was jailed last year for 11 years for subversion. US President Barack Obama - who was given the Peace Prize laureate in 2009 - called on Beijing to release the 54-year-old.
Chinese police stepped up patrols at key points, including Tiananmen Square, where witnesses say hundreds or thousands were killed when troops crushed reform protests.
The police presence was also heightened at the appartment where Liu's wife is believed to be under house arrest.
Western news websites appeared to have been blocked for a time.
At the ceremony Norwegian Nobel committee chairman Thorbjoern Jagland said: "If the country proves capable of developing a social market economy with full civil rights, this will have a huge favourable impact on the world. If not, there is a danger of social and economic crises arising in the country, with negative consequences for us all."
Norwegian actress Liv Ullmann read out an address made by Liu, who was closely involved in Tiananmen and more recently helped found the reform group Charter 08, to a court during his trial for subversion in December 2009.
"Hatred can rot away at a person's intelligence and conscience. (The) enemy mentality will poison the spirit of a nation, incite cruel mortal struggles, destroy a society's tolerance and humanity, and hinder a nation's progress toward freedom and democracy," the address said.
The Peace award, as often in the past, has stirred international diplomatic conflict, with China accusing the Committee of representing the interests of arrogant Western nations who seek to impose their ideas on an unreceptive world.
"The facts fully show that the Nobel Prize Committee's decision does not represent the majority of the world's people, especially the will of most developing countries. Prejudice and lies will not stand," the Chinese Foreign Ministry said.