UN chief Ban Ki-moon Thursday called for an end to attacks and discrimination against gays on the eve of the official opening of the Sochi Olympics, as the United States warned of toothpaste bombs on flights to Russia.
The build-up to the 22nd Winter Games has been overshadowed by concerns over security and human rights -- with a law passed last year banning the dissemination of "gay propaganda" to minors criticised by activists as vehemently homophobic.
Speaking as sporting action got under way on Thursday, Ban told a session of the International Olympic Committee in Sochi that everyone should join together to fight discrimination.
"We must all raise our voices against attacks on lesbians, gays, bisexual, transgender or intersex people. We must oppose the arrest, imprisonment and discriminatory restrictions they face," he said.
"I know principle six of the Olympic Charter enshrines the IOC's opposition to any form of discrimination."
"Hatred of any kind must have no place in the 21st century," said Ban, who did not specifically address the situation in Russia.
Russian Deputy Prime Minister Dmitry Kozak later denied there was discrimination in Russia and said there should be no gay rights protests at the Olympics.
"Political propaganda during sporting events is forbidden by the Olympic charter and Russian law," he said.
More than 200 leading international authors including Salman Rushdie, Margaret Atwood and Jonathan Franzen criticised the anti-gay law as well as blasphemy legislation as a "chokehold" on creativity, in an open letter published in Britain's Guardian newspaper.
And Russian punk protest group Pussy Riot defied President Vladimir Putin by calling for a "Russia that is free" at a star-studded New York concert where they were feted by Madonna and cheered by thousands.
Toothpaste bomb warning
As well as rights concerns, the Games have been stalked by fears of terror attacks.
The United States on Wednesday warned American and foreign airlines that militants could try to hide explosives in toothpaste tubes on Russia-bound flights.
An official told AFP that the US government has information "specifically targeting flights to Russia".
In a statement, the Department of Homeland Security said that "out of an abundance of caution" it regularly shares relevant information with partners both at home and abroad.
Two US warships have arrived in the Black Sea and will stand ready to offer assistance in the case of a security emergency at the Sochi Olympics, including the evacuation of Americans in the event of an attack.
Suicide bombings in the southern Russian city of Volgograd in late December killed 34 people and raised fresh concerns about the ability of the Russian authorities to ensure security during the Games.
Russian security forces are still fighting Islamist insurgents in the Northern Caucasus region, which is close to Sochi, and militants have threatened to strike targets in Russia during the Olympics.
About 40,000 members of the Russian security forces are on duty in and around Sochi in one of the tightest operations ever mounted at an Olympics.
'We have earned the right'
The Games are the biggest event that Russia has hosted since the fall of the Soviet Union and the project has been championed by Putin ever since the successful bid in 2007.
Workers were rushing to finish accommodation facilities, with some members of the media complaining their rooms were still a work in progress. But the government insisted Russia was ready.
Kozak said Russia had been waiting to host the Olympics again since the 1980 Moscow Summer Games, adding: "We have earned the right to host this celebration of peace and sport."
French skiing legend Jean-Claude Killy, the IOC's pointman for Sochi, said that Russia had delivered in "spectacular fashion" on its promises.
Friday's opening ceremony will be attended by more than 40 heads of state including Chinese President Xi Jinping and embattled Ukrainian President Viktor Yanukovych, who is facing protests at home and will hold crunch talks with Putin.
But no major Western leader is expected, in what many see as a snub to Russia over its rights climate.
Feuding neighbours Armenia and Azerbaijan have vowed to observe a ceasefire over the disputed Nagorny Karabakh region during the Games, mediators said.
Under stunning blue skies in the mountains above Sochi, British snowboarder Billy Morgan was the first competitor in action on Thursday.
Women's freestyle skiing got under way and alpine skiers began training while Russian skating icon Yevgeny Plushenko took to the ice in the team competition.