Three terrorists from the Xinjiang Uygur autonomous region who launched an attack in Beijing's Tian'anmen Square in 2013 were sentenced to death, while legal experts are calling for regulations against terrorism and extremism in the western China region.

Thirteen others who were involved in seven other cases were executed on Monday in connection with terrorist attacks and violent crimes.

A court in Urumqi, capital of Xinjiang, sentenced Husanjan Wuxur, Yusup Umarniyaz and Yusup Ahmat to death after convicting them of organizing and leading a terrorist group and endangering public security with dangerous methods.

Five other members of the group received prison sentences ranging from five years to life.

The group, formed in 2011, had plotted from December 2012 to September 2013 the attack that left three dead and 39 injured, according to the Urumqi Intermediate People's Court, where eight members of the cell had been tried since Friday.

Three members in the group - Usmen Hasan, his mother Kuwanhan Reyim, and his wife Gulkiz Gini - drove a jeep into a crowd of people near Jinshui Bridge, which crosses the moat of the Forbidden City, on Oct 28, 2013. The jeep crashed into a guardrail of the bridge, and the three in the jeep were killed when they set gasoline inside the vehicle on fire.

The cell members, who were influenced by religious extremism, were seen making a vow in front of a flag in the video footage shown at the court. Also, a flag related to religious extremism was recovered from the burnt jeep.

As religious extremism is believed to have led to an increasing number of terrorist attacks in Xinjiang and other parts of China, law experts from Xinjiang urged legislators to draft a regional regulation to deal with the growing problem.

"China and, more specifically, Xinjiang need to speed up drafting national and local laws and regulations to fight terrorism, and anti-extremism regulations should be treated as a crucial part of the anti-terrorism legislations," said Roz Simayi, president of the Xinjiang Law Association.

An anti-extremism regulation could help to tackle terrorism at its roots and prevent deadly attacks. The regional regulation could clarify what extreme religious activities are and authorities could handle such issues according to law, said Chen Tong, director of Xinjiang Normal University's law school.

"It (the regulation) could regulate the use of extreme religious symbols or clothing and provide the legal grounds to curb the spread of religious extremism," Chen said.

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