The final touches being made to the interior of the Australian pavilion on Tuesday. [China Daily]

China is confident of hosting a safe and successful World Expo, Shanghai's top leader has said in the aftermath of serial suicide bombings in Russia which have jolted the world.

With 30 days to go before the grand opening of the gala, Shanghai Party chief Yu Zhengsheng said the city can ensure the security of the 184-day event with the key being mobilization of people and careful implementation of plans.

"All the infrastructure will be completed in time; all measures on security, traffic and publicity have been taken, and residents have high expectations of the Expo - all of which show that we are ready," he said.

"I am confident that with the help of the public, we will do an excellent job on security," he added.

Security has become a paramount issue following Monday's double suicide bombings in Moscow, which killed 39. Another two suicide bombings in Russia's North Caucasus region on Wednesday killed at least 12.

Major Chinese cities have stepped up security checks at subway stations while some propose upgrading checks at bus stations.

Beijing on Tuesday beefed up security in the city's metro system.

Fu Zhenghua, director of the Beijing public securit bureau, said police patrols with sniffer dogs were increased at metro stations, where they will make more frequent checks.

Many believe the Expo faces tougher security challenges compared to the 2008 Beijing Olympic Games due to the six-month duration and huge number of visitors, estimated at 70 million.

Pan Guang, an expert on anti-terror affairs at the Shanghai Academy of Social Sciences, said for any big event, vigilance tends to wane as it draws on.

Li Wei, director of the anti-terrorism research center at the China Institute of Contemporary International Relations, said security threats could come from anywhere, such as from "East Turkistan" terrorist organizations seeking Xinjiang "independence".

Shanghai has taken such measures as extending the X-ray scanning of passengers' hand luggage to all metro stations.

City officials are also hoping to close a deal with Swedish security services provider Securitas AB.