Beijing: China seems to have expanded the use of high-security detention centres as a tool of repression in Tibet, according to a new study by the Rand Europe research institute using 'night-time lighting'.

The precise workings, nature and scale of the Chinese Communist Party's efforts to imprison and detain Tibetans, however, remain poorly understood. This study, therefore, aimed to build on the scant available evidence and leveraged an innovative method — night-time lighting data — to shed light on the prisons and detention facilities in Tibet.

Measured on a daily basis using satellite-based sensors, night-time lighting data represent an equilibrium measure of electricity consumption at night at specific locations over time. Aggregated into monthly trends, these data can help illuminate potential changes in the construction, growth or decline in the use of specific detention facilities across Tibet that may not be visible using overhead satellite imagery alone.

The report revealed that Chinese authorities, as part of their nationwide 'stability maintenance' strategy, are detaining, persecuting and convicting Tibetans for non-violent forms of protest and other expressions of dissent such as assisting or supporting self-immolations and carrying pictures of the Dalai Lama.

The report described the Tibetan detention system as a "black hole" to the international community.

According to the Rand Europe research institute, currently, there are at least 79 prisons and detention centres throughout Tibet, with most towns and villages having detention centres.

There has been a pattern of increased activity in recent years at high-security detention facilities in Tibet, according to a new study.

"Our analysis of overhead satellite imagery suggests that 86 per cent of all detention facilities in the Tibet Autonomous Region (TAR) were built by 2011 at the latest, although this is an imperfect measure owing to gaps in the availability of archival imagery before this date. This figure is based on the first year in which specific detention facilities are visible in available commercial satellite imagery — an imperfect measure of the date of construction, but still instructive in assessing when widespread Tibetan detention was first conceived and implemented," the report read.

"Although we cannot rule out the possibility that Tibet's former Party Secretary Chen Quanguo may have repurposed existing facilities for political purposes upon his arrival, we can hypothesise (but not conclude) that the construction of these facilities reflects policy and managerial objectives rather than one individual's leadership style," the report added.

Since Chen's tenure, the overall size and scale of the Tibetan detention system have been relatively stable, which suggests ongoing continuity in government policy.

Tibet has been under Chinese control since it was annexed more than 70 years ago, in what Tibetans describe as an invasion and what Beijing claims was a peaceful liberation from theocratic rule.

There have been successive waves of government crackdowns, including the campaign against Tibetans. Several activists and human rights groups have expressed growing concern over the harassment, detention and torture of Tibetan activists, religious figures, and intellectuals, as well as mass surveillance of the population, and programmes of mandatory re-education and labour transfer, according to the report.