Officials on Wednesday said this week's attack on a police station in China's far western Xinjiang region had been “masterminded” by terrorist groups, while security analysts here suggested separatist groups active in Pakistan had a role in the violence.

Officials raised the death toll from Monday's attack in Hotan, a city in southern Xinjiang, to 18. While police shot down 14 “rioters”, four others, including two women, were killed in the attack.

Hou Hanmin, the head of the regional information office in Hotan, told The Hindu in a telephone interview that the attackers were “organised”, and armed with knives and grenades.

The rioters had entered a nearby government office before attacking and setting fire to a police station. They had taken six hostages before the police shot 14 of the 18 reported attackers, according to official accounts.

“They held up a banner calling for ‘holy war',” said Ms. Hou. “The attack was brutal and ruthless. This was clearly an attack masterminded by terrorist groups.”

Xinjiang has seen intermittent unrest with clashes between the local Uighur ethnic group and the increasing number of Han Chinese, the country's majority ethnic group, who have migrated to the region in recent years. The government has, in the past, blamed Uighur separatist groups for the clashes, though many Uighurs say tensions had been driven by rising inequalities between the groups.

On Wednesday, government-run newspapers quoted terrorism experts as saying the attacks were carried out by separatists, likely linked to terror groups active in Pakistan. Xinjiang shares a border with Pakistan-occupied Kashmir (PoK).

“Located in the southern part of Xinjiang, Hotan is close to the border with Pakistan. Due to their affinity in religion and language, some Uighur residents there are at risk of being influenced by terrorist groups such as the East Turkistan Islamic Movement (ETIM),” Pan Zhiping, director of the Institute of Central Asia at the Xinjiang Academy of Social Sciences, told the Communist Party-run Global Times.

He said Hotan “appears prone to the influence of terrorism that has penetrated the country from overseas”.

Li Wei, an anti-terrorism expert with the China Institute of Contemporary International Relations (CICIR), told the same newspaper that “signs have shown that the rioters were greatly influenced by overseas terrorist organisations”.

The East Turkestan separatist movement was “very active on the soil of Pakistan”, Zhao Gancheng, a South Asia scholar at the Shanghai Institute for International Studies, told The Hindu. But China and Pakistan, he said, had kept “good communications on this issue”.

Ms. Hou said the investigation was “on-going”. The national counter-terrorism office had dispatched a working team to Hotan.

“There is no sign that this incident is linked to any Pakistan-based terrorist groups,” she said.

But overseas Uighur groups questioned the government's version of events. An exiled Uighur group called the World Uyghur Congress said on Wednesday this week's clash was sparked by a protest by local residents who had called on the police to release information about their missing relatives, believed to be in police custody.

Ms. Hou, however, said there had been no protest earlier this week.

She rejected reports that the attack was an ethnic conflict. “Both Han and Uighur people were hurt,” she said. An Uighur security guard and an Uighur police officer were among those killed by the attackers.

“This was not a clash between ethnic groups, and has done enormous damage to the local community.”

Many Uighur groups have, in the past, accused the government of portraying local protests and ethnic unrest as being driven by separatist groups in order to justify security clampdowns.

In 2009, the government blamed overseas groups for orchestrating ethnic riots between Uighurs and Han Chinese in the city of Urumqi, which left more than 197 people dead. However, dozens of the city's residents, in interviews with The Hindu last year, blamed long-standing distrust between both ethnic groups, driven by increasing migration and rising inequalities, as sparking ethnic tensions.

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