A massive manhunt is under way for a man police believe shot and killed a railway police officer on Friday.

The suspect, Zhou Kehua, who is also the suspect in a series of robberies and killings dating to 2004, is thought to have committed his latest homicide when the officer was patrolling a section of railway in Chongqing on Friday afternoon, according to an officer from the Chongqing public security bureau who did not want to be identified.

The attack has intensified the fears that have been stoked by the 42-year-old gunman's alleged crimes. He is believed to target people who are withdrawing money from banks and has become adept at dodging police manhunts.

The search for Zhou has been going on since Friday morning, when he is suspected of having killed a woman and injured another two in a robbery in which he is thought to have stolen 250,000 yuan ($39,300) from the victims.

By Sunday afternoon, large numbers of police officers, Armed Police Force officers and People's Liberation Army soldiers were combing the slopes of Geleshan Mountain, where Zhou is believed to be hiding. As part of the search, notices offering rewards for clues to Zhou's whereabouts have been posted in almost every street in urban parts of Chongqing and police have established checkpoints on many large streets and at tollgates on highways.

The Chongqing police are offering a 500,000 yuan reward for tips leading to Zhou's capture dead or alive.

The Ministry of Public Security has classified Zhou as a "class-A" suspect. In all, 5.4 million yuan in rewards are being offered for tips leading to his capture, according to media reports.

On Geleshan Mountain and in its environs, police officers have been dispatched in groups stationed 50 meters apart on roads leading up and down the mountain. A large number of officers, meanwhile, were standing at the top of the mountain road.

A publicity officer from the Chongqing police declined to release new information about the search for Zhou, who is suspected of killing 10 people in Chongqing, Nanjing and Changsha since 2004, including the police officer and the woman who died on Friday.

In the hunt, the police have had to battle against temperatures as high as 40 C and the dense bushes and forests of Geleshan Mountain. Their search has uncovered a mountain cave that Zhou is believed to have stayed in. Inside it were two cigarette cases, a T-shirt and human waste. Media reports said police extended their hunt to Chongqing's Tongliang and Bishan counties on Saturday morning.

Wu Changming, a 52-year-old resident of Geleshan township, said police officers in the township are on guard 24 hours a day.

Relatives of the two people who were injured in the shooting on Friday declined to be interviewed on Sunday. The victims are receiving medical treatment at a hospital in Chongqing.

Previous media reports have described Zhou as cunning and ruthless, a man who never stays in hotels and is capable of surviving in the wild.

A police source in Nanjing, Jiangsu province, has confirmed that Zhou is also suspected of having committed a shooting and robbery in Nanjing in January, the news website people.com.cn reported on Friday.

Zhou is believed to have shot and robbed a man in front of a bank on Nanjing's Dongmen Street on Jan 6 just after the man had withdrawn 200,000 yuan.

Media reports have also said Zhou served a short prison term in Yunnan province in 2005 after he had been found guilty of trafficking firearms.

Timeline

Since 2004, Zhou Kehua is suspected of being involved in a series of robberies and shootings.

April 22, 2004

One woman was shot dead and another woman injured in a bank robbery in Jiangbei district, in Southwest China's Chongqing. The suspect took 70,000 yuan ($11,005).

May 16, 2005

Two suspects shot and robbed a couple near a bank in Shapingba district in Chongqing. A passer-by was also shot. The couple died. The suspects made off with 170,000 yuan.

March 19, 2009

A People's Liberation Army soldier standing guard outside a garrison in Chongqing was shot dead. The victim, identified as 18-year-old Han Junliang, was shot twice in the chest with a pistol. The suspect took the garrison guard's submachine gun and ran.

Oct 14, 2009

A 56-year-old farmer was shot dead in a park in Tianxin district of Changsha, capital of Central China's Hunan province. The suspect used a homemade gun.

Dec 4, 2009

A 41-year-old man was shot dead outside a bank in Tianxin district of Changsha. The victim had withdrawn cash and was walking to his car when the suspect shot him in the head. The suspect took 45,000 yuan from the man.

Oct 25, 2010

A trading company owner was shot dead in Yuhua district of Changsha.

June 28, 2011

A 48-year-old businessman was shot in the head and stomach as he got out of his car near a construction site in Tianxin district of Changsha. The man was taken to a hospital and survived.

Jan 6

A 42-year-old man was shot in a robbery in Nanjing, Jiangsu province. He was robbed shortly after he withdrew 200,000 yuan from a bank in the Xiaguan district. The suspect fled the scene by jumping into a vehicle. The victim died in a hospital.

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