BEIJING, Nov 18 (AFP) - The Communist Party's top official in Tibet has accused hostile foreign forces of targetting the region's youth in their bid to infiltrate and split Tibet from the rest of China.

"Hostile forces at home and abroad, in schools and society at large, are using illegal measures to seize our youngsters away from us," Tibet party secretary Chen Kuiyuan was quoted as saying in a press report seen here Monday.

In a separate development Monday, a human rights watchdog reported that an imprisoned Tibetan nun, whose original conviction was declared unlawful by a US committee, had had nine years added to her jail term for insubordination.

Chen's remarks, published on the front page of the Tibet Daily, were made last week at the close of an extraordinary meeting of the region's top leadership.

The meeting had called for the launch of a final battle against the Dalai Lama, Tibet's exiled spiritual leader.

Chen said that separatist forces headed by the Dalai Lama "are using their religious influence and the western media ... to spread ideas of 'Tibetan independence," splitting public opinion and creating turmoil."

He warned that teenagers in schools, monasteries and nunneries had become the prime focus of the Tibetan separatist movement in finding new supporters for its cause.

"We must take patriotic and socialist education as the keystone of ideological construction in Tibet," Chen said.

The leadership meeting, which ended November 8, confirmed a major religious crackdown in Tibet after warnings that regional officials had lost their way and were not following the party line.

"Such problems have reached such a serious level that they pose a direct threat to the stability and development of Tibet," Chen said.

While stressing that the government would not interfere in "normal" religious activities, Chen stressed that religion in Tibet had to be viewed from a "Marxist viewpoint."

"Religious idealism is the main obstacle to the development of spiritual civilisation in Tibet, and we must never allow the resurrection of feudal priviliges in monasteries," he said.

The phrase "spiritual development" was coined by President Jiang Zemin and has already been used as justification to crack down on the "backward" culture of China's Moslems in Tibet's neighbouring region of Xinjiang.

Meanwhile, the London-based Tibet Information Network (TIN) reported Monday that jailed Tibetan nun, Ngawang Sangdrol, 19, had been sentenced to a further nine years for refusing to stand up in front of a prison guard during a re-education drive in Lhasa's Drapchi prison.

She was also charged with shouting "Free Tibet" during a punishment period, TIN said, citing unofficial sources.

The extra term was announced on July 31, the sources said. Sangdrol, who comes from Garu nunnery five kilometers (three miles) north of Lhasa, will have the new sentence added to the two she is already serving three years for taking part in a 1992 pro-independence demonstration and six years for singing nationalist songs in prison in 1993.

The accumulated sentence of 18 years means Sangdrol is now facing a longer term in jail than any other female political prisoner in Tibet, similar in length to the sentences served by Tibetans in the "hardline" era of the 1960s and 1970s.

In November last year, the UN Working Group on Arbitrary Detentions, which assesses reports of illegal imprisonment, ruled that the continuing detention of Sangdrol was arbitrary because she had been punished for exercising her right to freedom of opinion.

The committee asked China to "take the necessary steps to remedy the situation in order to bring it into conformity with the provisions and principles incorporated in the Universal Declaration of Human Rights."