(CNN) -- The death toll of Saturday's explosion at a McDonald's outlet in China has gone up to two, after a weekend that saw five others die during a series of similar incidents in a southern province.
Beijing has asked regional authorities to conduct a thorough security check in the wake of the incidents in Shaanxi and Guangdong provinces.
Apart from stepping up surveillance on criminal gangs, a key goal of this year's winter security campaign is to prevent violent and terrorist activities.
China's official media have reported that the violent acts were committed by individuals rather than groups or organizations.
However, sources close to security departments in Beijing said the authorities were investigating whether the recent bombing incidents and other violent acts not reported in the media had links to terrorist and "cult" groups including Xinjiang separatists and the Falun Gong.
They said police nationwide were on alert against Uighur separatists who might stage acts of retaliation against the arrests of more than 2,000 underground activists in southern and western Xinjiang since mid-September.
Suspect Xian has a sizeable population of Uighurs and the lone suspect behind the McDonald's bombing was reported by local police to be somebody from outside Shaanxi Province.
Several official papers also reported that the McDonald's incident was a case of "suicide bombing" and that the suspect was killed on the spot.
At the same time, internal party and government circulars have identified the Falun Gong spiritual movement as a "terrorist organization."
And the state media on Monday gave a big play to the story of Falun Gong practitioner Fu Yibin, who allegedly stabbed his father and wife to death late last month.
The official China News Service reported on Monday that police in Shaanxi were carrying out extra checks in an effort to prevent fires, explosions, as well as "violent and terrorist activities."
The special security alert would last at least through to the Chinese New Year in mid-February.
Officials in Guandong said over the weekend that the explosions that killed five and injured seven in the cities of Zhanjiang and Jiangmen were perpetrated by Lin Guojian.
They said Lin, who died while setting off a detonation, had had arguments with some of his victims over money and emotional issues.