Kathmandu, Nepal (CNN) -- A U.S. citizen holding a "Free Tibet" banner has been turned back from the slopes of Mount Everest, a Nepalese army officer said.

The incident comes as authorities in Nepal tighten security on Mount Everest in advance of the scheduled arrival of the Olympic torch in early May.

An international torch relay has been dogged by pro-Tibet protesters in several cities around the world. The Olympic flame arrived in Australia on Wednesday morning after a relatively incident-free run in Indonesia.

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The U.S. citizen was turned back Monday, the army officer told CNN on condition of anonymity.

Nepal strictly controls anti-Chinese activity on its soil and has deployed troops on the world's highest peak. Organizers plan to take the Olympic torch to the summit of Everest in early to mid May.

Nepal has about 25 security personnel on the mountain, including 15 soldiers trained in mountain warfare, the army officer said. Security forces on the mountain have permission to shoot mountaineers engaged in anti-Chinese activities, according to a Home Ministry official. E-mail to a friend

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