China opened the railway to Tibet's capital Lhasa in 2006, which passes spectacular icy peaks on the Tibetan highlands, touching altitudes as high as 5,000 metres (16,400 feet) above sea level, as part of government efforts to boost development.
Critics of the railway, including exiled Tibetans and rights groups, say it has spurred an influx of long-term migrants who threaten Tibetans' cultural integrity, which rests on Buddhist beliefs and a traditional herding lifestyle.
The Global Times, published by the ruling Communist Party's official People's Daily, said that an extention to Shigatse, the traditional seat of Tibetan Buddhism's second-highest figure, the Panchen Lama, would formally open next month.
That link is scheduled for its own extension during the 2016-2020 period to two separate points, one on the border of Nepal and the other on the border with India and Bhutan, the newspaper cited Yang Yulin, deputy head of Tibet's railways, as saying, without providing details.
China has long mooted this plan, but the difficulty and expense of building in such a rugged and remote region has slowed efforts.
Tibet is a highly sensitive region, not just because of continued Tibetan opposition to Chinese control, but because of its strategic position next to India, Nepal and Myanmar.
The Chinese announcement coincides with a drive by India, under its new prime minister Narendra Modi, to consolidate its influence with its smaller neighbours.
Modi's foreign minister, Sushma Swaraj, heads to Nepal on Friday with a proposed pact to help develop the Himalayan country's hydro-electric power potential high on the agenda.
Modi, who made his first foreign trip as prime minister to Bhutan, is to visit Nepal next month. But Nepal's opposition Maoists are uneasy about the hydro-electric plan and say it could lock out China to the benefit of Indian companies.
India and China fought a brief border war in 1962 over the region at the eastern end of the Himalayas. The nuclear-armed neighbours signed a pact in October to ensure that differences on their shared border do not spark a confrontation.
India and China have competing claims over what India calls Arunachal Pradesh, which has been administered by India for decades and what China calls South Tibet.
China's Communist army occupied Tibet in 1950. Nine years later, Tibet's spiritual leader, the Dalai Lama, fled to India after a failed uprising.