Five suspects "blew themselves up" in the attack on an open market in China's Xinjiang region which killed 31 people on Thursday, state media reported.

The Global Times newspaper said police were investigating whether more accomplices were at large after assailants in two vehicles ploughed into shoppers and traders and threw explosives at a street market in Urumqi, the capital of Xinjiang.

The attack was described by authorities as the latest "severe terrorist incident" to hit the far-western region, home to China's mainly Muslim Uighur minority.

China has seen a series of incidents in recent months targeting civilians, sometimes far from Xinjiang itself, which authorities have blamed on separatists from the region.

Critics of Beijing's policies in Xinjiang say that tensions in the region are driven by cultural oppression, intrusive security measures and immigration by majority Han Chinese which have led to decades of discrimination and economic inequality.

'Sinister new pattern'

Al Jazeera's Adrian Brown, reporting from Urumqi, said the city appeared calm after the attack but there were high-profile police patrols at all key intersections.

"What really worries people here is they feel that the market was a really soft target, they were just ordinary Han Chinese going about their business when two vehicles ploughed into a crowd," he said.

Inside Story - Chinese Uighurs: separatism vs terrorism?

"China is not used to seeing this type of violence. It is a sinister new pattern that is beginning to emerge."

Some of the shoppers returning to the area on Friday said doing so was an act of defiance.

One elderly woman told the AFP news agency: "Just because people come here and try to terrorise us, it does not mean I should have food which is not fresh."

Meanwhile, the China Daily reported on Friday that authorities were boosting security in the capital "after a series of terrorist attacks across the country".

It said a new patrol plan, covering the skies, subways and streets, was to be implemented in 14 areas, including popular shopping districts and the Beijing Railway Station.

"Once an emergency happens, nearby armed police will take one minute to rush to these areas," the paper quoted Zhang Bing, deputy director of Beijing Public Security Bureau, as saying.

Source: Al Jazeera and agencies