Police in Kashi, Northwest China's Xinjiang Uyghur Autonomous Region have stopped  a terrorist attack, in which 21 people including six terrorists were killed.

The attack in Serikbuya town, Bachu county, took place at 1:30 pm Tuesday, local news portal ts.cn first reported on Wednesday.

Terrorists killed 15 police officers and community workers, among whom 10 were Uyghur, three were Han and two were Mongolian. Police fought back, killing six terrorists and arresting eight, with the attack now under full investigation.

A senior official from Xinjiang, who asked not to be named, disclosed Wednesday some details about the attack to the Global Times.

According to initial information, the group had been working on an elaborate attack plan, and was involved in extreme religious activities. "They watched videos from overseas showing terrorist acts and underwent physical training," said the official.

On Tuesday, when three community workers paid a regular visit to a house the group was staying in, they caught the terrorists watching such a video and found a cache of weapons. The community workers contacted the police while trying to defuse the situation but the terrorists stabbed them to death.

Receiving the report, the local police chief led a team to investigate the scene but they were ambushed by the terrorists. The police chief apparently discharged his firearm in response to the threat but the squad was cornered in a room of the house.

The official told the Global Times that the terrorists barricaded the door, doused it in petrol and set it alight, burning the police officers and community workers in the team to death.

The details were confirmed by an anti-terrorism official in Kashi to the Global Times.

Hou Hanmin, spokesperson for the regional government, told the Global Times that the killing showed obvious features of a terrorist attack.

"Terrorists wouldn't care about victims' ethnicity or nationality, nor about whether they were officials or members of the public," Hou said, citing the recent Boston marathon bombing and foiled plot to derail a New York-to-Toronto train. "Terrorists are the common enemies of peace-loving people across the world."

Xinjiang has witnessed a number of terrorist attacks in recent years, with the most deadly one taking place on July 5, 2009 in the regional capital of Urumqi, leaving 197 people dead and more than 1,600 others injured.

This latest one took place in Serikbuya, 260 kilometers away from Kashi.

A local restaurant owner surnamed Wang told the Global Times that most shops remained closed on Wednesday, as the attack had provoked an intense panic.

A teacher surnamed Guo told the Global Times that the large number of deaths had left a deep "psychological trauma" both for him and local residents, but he believed order would be restored as security was being tightened.

Pan Zhiping, a professor with Xinjiang University, told the Global Times that Xinjiang is the frontline in China's fight against terrorism.

"Terrorist acts in the region threaten the security and stability of the entire country. We must resolutely root out terrorism," he said.

An anti-terrorism expert from the Special Police College of the Chinese People's Armed Police Force told the Global Times that terrorists in Xinjiang are growing more "professional" in plotting attacks, and that anti-terrorism forces should raise their vigilance accordingly and become better equipped.

A crisis management expert, speaking under condition of anonymity, agreed and added that the casualties in this latest attack were "too high a price to pay." "Under the current precautionary system in Xinjiang, those with no professional capacity like community workers are put on the frontlines of the fight against terrorism. Finding ways to ensure their safety is an urgent problem to be solved," he told the Global Times.

One security official told the Global Times that East Turkestan separatists and the East Turkestan Islamic Movement (ETIM), a terrorist group listed by the UN, have been connected with Al Qaeda since their establishment and share supplies with them.

According to Pan, in addition to terrorist attacks carried out in Xinjiang, East Turkestan separatists also joined terrorist acts in Chechnya, Afghanistan and Syria.

"However, the West has been holding double standards in the definition of terrorism. If the East Turkestan separatists carry out evil deeds in Xinjiang, some Western opinions whitewash them as seeking 'national self-determination.' Only when their acts threaten their domestic security would Western countries change their attitudes," Pan said.

Liu Chang and Bai Tiantian contributed to this story