At least 19 people have been detained by authorities in China’s far western Xinjiang region, in connection with last week’s violence which left 21 people killed.

Eleven people, described by authorities as “runaway suspected terrorists”, had been captured, officials said late on Monday, in addition to eight other suspects who were detained at the scene of the violence last week.

Ten police officers and five community volunteers were killed in the violence in Bachu, in the prefecture of Kashgar which is in Xinjiang’s western frontier and borders Pakistan-occupied Kashmir.

Six others, described by officials as “gangsters”, were shot dead by police following the violence on April 23.

Authorities alleged on Monday that the suspects were part of “a terrorist group” founded in September of last year and were planning to carry out an attack in Kashgar in the summer.

Kashgar – the name of both the famous Silk Road town near China’s western border as well as the prefecture it is located in – has been the scene of intermittent violence and ethnic unrest between the Uighur minority of Xinjiang and Han Chinese migrants, particularly after the riots of 2009 in Urumqi, the regional capital, which left at least 197 people killed.

Around 40 people were killed in 2011 in a series of knife attacks carried out in populated markets and restaurants in the cities of Kashgar and nearby Hotan. Chinese authorities blamed those attacks on Uighur groups with ties to terrorist groups based in Pakistan, such as the separatist East Turkestan Islamic Movement (ETIM).

Officials said on Monday that the group behind last week’s attack had gathered to “regularly watch video clips advocating religious extremism and terrorism” and attended “illegal preaching ceremonies”.

They alleged that in March, the group had made explosive devices and tested them. The authorities said the violence last week was triggered after community workers had spotted the group “making explosives”.

Meng Hongwei, Vice Minister of Public Security, said on Monday that the police “tracked down a batch of homemade explosives, lethal weapons, and flags of ‘East Turkestan’ terrorists after the April 23 clash”, the official Xinhua news agency reported. He also pointed to “incessant incitement and influence from overseas ‘East Turkistan’ secessionist terrorists” as stirring the violence.

Many Uighurs in China have, however, accused the government of exaggerating the terrorism threat and using it to impose security restrictions. Recent campaigns in Kashgar and Hotan to discourage “illegal” religious activities – such as private study sessions and any gathering outside State-sanctioned mosques – and to ban government workers and students from wearing veils and growing beards have been strongly criticised by Uighur groups.

The 15 police officials and community workers killed last week were on Monday honoured by the government as “regional anti-terrorist heroes”.

They included 10 Uighurs, three Han Chinese and two ethnic Mongolians.

At a ceremony to award them posthumously, Xinjiang Governor Nur Bekri said last week’s violence “was not about ethnic or religious issues, but a terrorist act to split the motherland and undermine national unity”.

“It is a political fight between separatism and anti-separatism, and between safeguarding the national unity and undermining the national unity,” he said. “We will leave no room for compromises and concessions.”

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