BEIJING (Reuters) - Guaranteeing security is the top priority of the Beijing Olympics, Chinese President Hu Jintao has said, and a mobilisation order has gone to national paramilitary troops telling them to ensure a trouble-free Games.

Hu and other leaders did not mention worries about protests, riots and terrorist threats on Monday at the lighting of the Olympic Games torch in Beijing, but on Tuesday the official newspaper of China's anti-riot forces spelt out their concern.

"Security must take priority," Hu told officials, according to the People's Armed Police news.

"Without security guarantees there cannot be a successful Olympic Games, and without security guarantees the national image will be lost."

The paper also released a "political mobilisation order" to the People's Armed Police (PAP) troops telling them to prepare for an arduous time ensuring order and control before and during the Games, which are held in August.

"The drums of war are sounding, a decisive battle is at hand. For the sake of the Chinese nation's image and for the honour of the People's Armed Police, let us never forget our duty."

The official warnings come in the wake of anti-Chinese riots and protests in Tibet and nearby western provinces in March, and after international rights groups vowed protests at the Games to highlight their complaints about China's policies on human rights and media controls, Sudan's Darfur region, and Tibet.

China has also said it has foiled terrorist acts by Uighurs seeking an independent homeland for their largely Muslim people in the western region of Xinjiang.

Security spending for major sporting events have soared since the September 11 attack on the United States, but China has said that by using its own personnel and technology it can hold a safe Olympics for a fraction of the $1.8 billion spent on the 2004 Athens Games.

Saturation security at the torch-lighting ceremony kept ordinary citizens well away from the capital's Tiananmen Square and underscored China's fears of any unrest or protest sullying the Games, on which the government has spent billions in show of national prosperity and confidence.

China's top domestic security official, Zhou Yongkang, is second-in-command of a Communist Party team overseeing preparations for the Games.

The commander of the PAP Beijing force, Ma Bingtai, told the paper that troops face "many conflicts and challenges".

The paramilitary force is dedicated to ensuring domestic order in the one-Party state. It has also been intensely involved in quelling unrest and violence among Tibetans protesting against Chinese policies and economic influence.

The PAP has 660,000 troops, the government said in 2006.

Even before the Olympic torch arrived in Beijing on Monday, it drew protests from critics abroad. And with the torch now on a 130-day trek across the world from the Chinese capital, more demonstrations abroad are certain.

(Take a look at the Countdown to Beijing blog at http://blogs.reuters.com/china)

(Reporting by Chris Buckley; Editing by Nick Macfie and David Fox)