Police in Shanghai on Monday vowed to crack down on credit card fraud by foreigners as statistics revealed that large-scale international fairs like the Expo tend to attract card scammers to the host city.

Police arrested six foreigners last week withdrawing a total of 190,000 yuan ($27,800) from the city's ATMs using phony cards.

Dai Xinfu, deputy head of the economic crime investigation department of the Shanghai Public Security Bureau, said at a news conference on Monday that his department had learned from the Beijing police's experience during the 2008 Olympic Games and had taken a series of steps to counter any crime wave.

That involves monitoring expats in the city who have committed credit card fraud within the past three years, asking the Ministry of Public Security to provide the department with countrywide foreign crime information and monitoring ATMs and POS payment machines in the Expo Garden and major commercial areas.

"International credit card fraud rings are highly likely to move into Shanghai," said Dai. "During the Expo, credit card use will rise sharply. Foreigners visiting the city who are not familiar with ATM and banking systems here are more vulnerable to fraud."

Card fraud had increased at previous Expos, including the ones in Japan and Spain, said Dai, adding that the Shanghai police will do their best to counter the trend.

In the first quarter of this year, Dai's department cracked 999 credit card fraud cases, detained 385 suspects and retrieved more than 10 million yuan, according to police.

The 103 ATMs and bank outlets at the Expo Garden - all from the Bank of Communications - will be watched closely by police, as will ATMs in popular shopping malls, Dai said.

According to police, foreign credit card scammers have two ways of committing crimes.

"The more common way is to get personal credit card information from abroad before they arrive in the city, make fake cards here based on that information and withdraw money from ATMs with the fake cards," Dai said.

In other cases, Dai said, some female scammers become prostitutes to get the victims' credit card information and then use it to book hotels and airplane tickets online.