BEIJING, May 22  -- Chinese President Xi Jinping pledged to severely punish terrorists and spare no efforts in maintaining stability in response to Thursday morning's fatal explosions in Urumqi.

Two vehicles without license plates drove through roadside fences and plowed into people at an open air market at Gongyuanbei Street near Renmin Park at 7:50 a.m. and set off explosive devices, killing at least 31 people. More than 90 others were injured.

Xi ordered the police to step up patrols and security control over possible terrorist targets and prevent ripple effects.

He also asked local authorities to solve the case fast, put the injured under proper care and offer condolences to families of the victims.

He urged hard strike on violence and terrorists so as to safeguard social stability.

Chinese Premier Li Keqiang, meanwhile, called on authorities to step up safety measures and eliminate weak points in public security, to protect people's lives and properties.

A working group led by Minister of Public Security Guo Shengkun has left for Xinjiang to supervise the investigation and handle the aftermath.

So far all injured people have been sent to hospitals and police are pushing through the investigation, authorities said.