When China put 13 people to death in one day for terrorism offences in mainly Muslim Xinjiang, it raised the spectre of the mass executions of years past. But experts say Beijing's "strike hard" campaign is unlikely to curb mounting violence.

The 13 were executed on Monday in connection with seven different cases, the official Xinhua news agency said, including a riot in Lukqun last June when "knife-wielding mobs" attacked police stations, a government building and a construction site and set cars ablaze before officers opened fire. A total of 24 police and civilians were killed with 11 attackers also dying, according to previous Xinhua reports.

The executions came on the same day a court in the regional capital Urumqi sentenced three people to death over a fiery car crash last October that killed two tourists in Beijing's Tiananmen Square, the symbolic heart of the Chinese state, along with the trio in the vehicle -- a man, his wife and his mother.

Resource-rich Xinjiang, where mostly Muslim Uighurs are the largest ethnic group, borders Central Asia far from China's heartland, and has long seen sporadic clashes.

Rights groups accuse authorities of cultural and religious repression that feeds dissent in the region, while Beijing counters it has invested heavily in economic development in the area.

Recently, violent incidents have escalated in scale and spread, with a horrific knife assault at a railway station in the distant southern city of Kunming leaving 29 dead and 143 wounded in March, and 39 civilians killed and more than 90 wounded in an attack on an Urumqi market last month.

- 'Bloody agenda of terror' -

The development has alarmed authorities and Xinhua hailed the executions and sentences in a commentary Tuesday, arguing that "to fight such crime, China must mobilise all the people and use all legal weapons to deal a crushing blow".

"Only the rule of law will protect the people from the bloody agenda of terror... Anyone who breaks the law, threatens life or property, any separatists, will be severely punished," it wrote.

Yet death penalty experts and campaign groups say that while harsh punishments and public sentencing rallies may help the government garner attention, such moves actually do little to reduce the likelihood of further violent attacks.

"The death penalty may work in those cases where someone is committing a crime and thinking rationally," said Surya Deva, a professor at the City University of Hong Kong and an expert on Asia's use of the death penalty. "But in many of these crimes, these elements are not there.

"Capital punishment is not going to work against the potential terrorists because these people are already willing to die."

The recent crackdown and now-unusual public announcement of as many as 13 executions have echoes of China's past mass-sentencing drives -- which were popular throughout the tumultuous Cultural Revolution and, more recently, in a series of occasional "strike hard" anti-crime campaigns that began in 1983.

Authorities would sometimes parade criminals through the streets before executing them with a bullet to the back of the head.

One campaign in 1999 saw the southern province of Guangdong hold 57 public rallies to announce sentences for 818 convicted criminals.

Another in 2001 saw 89 convicts executed in one day across the country -- one of the highest single-day tallies on record for China, which puts more people to death annually than the rest of the world combined, according to the human rights group Amnesty International.

- Anti-crime credentials -

China has since largely adopted lethal injection but occasionally there are echoes of such events, as when four southeast Asian gangsters were shown live on state television last year being taken away for execution for the murder of 13 sailors on the Mekong.

The approach may allow ruling Communist Party leaders to burnish their anti-crime credentials, but "it doesn't really deliver the stability" they aim for, according to Anu Kultalahti, China researcher for Amnesty.

Recent highly-publicised "speed trials" -- such as May's mass sentencing of 55 people before a 7,000-strong crowd in a Xinjiang stadium -- suggest that Chinese authorities "have been more concerned about public opinion than delivering justice", she said.

Chinese courts are controlled by the ruling Communist Party and have a near-perfect conviction rate.

"The strike-hard campaign is not new to Xinjiang at all," said Shan Wei, a political scientist at the National University of Singapore's East Asian Institute. "If you search this keyword online, you see it almost every year.

But, he added: "The trend is, the violence is getting more and more terrorism-oriented.

"Before, in past years, before the Tiananmen attack, most targets were government buildings or police stations. But now, you can see more and more, the target is ordinary people."