* Machines to use face recognition technology
* Measure introduced as a top Chinese leader visits
* Police conduct raids to "purify environment" (Adds police comment on raids)
HONG KONG, May 8 (Reuters) - Macau plans to add security features to ATMs to monitor withdrawals, authorities in the world's largest gambling hub said as the Chinese territory seeks to tighten restrictions on cash flows out of the mainland.
Macau is a special administrative region of China and the announcement of the plan coincides with a visit by Zhang Dejiang, the head of China's parliament and its third-most powerful leader.
The new measures announced for China's UnionPay bank card means users will have to scan their identity card at automated teller machines (ATMs), which will use facial recognition technology to verify the user, the government said in a statement.
The government did not say when the changes would be implemented, but specifically mentioned ATMs around casinos.
Zhang is visiting Macau from May 8-10, and over the past nine months, Macau's gambling revenues have rebounded as more mainlanders take advantage of an easing of President Xi Jinping's campaign against shows of wealth by public officials.
Ahead of his visit, police in the former Portuguese colony raided casinos, cafes and bars, investigating a total of 790 people, to "purify the environment in the community and do the best to maintain safety and stability", the Judiciary Police said in a statement on Monday.
Those being investigated were suspected of various offences including illegal residence in Macau, human trafficking and illegal business operations.
In a bid to support the yuan, China's government has since late-2016 put in place capital controls that make it harder for individuals and companies to move money out of China.
A 2014 Reuters investigation found that many mainland Chinese use state-backed UnionPay cards to circumvent cash withdrawal limits of 20,000 yuan ($3,200) a day, and either use that money to gamble or transfer it abroad.
Customers open multiple bank accounts, and then withdraw cash from each, or use pawn shops in Macau to make fake purchases, the investigation found.
The planned ATM measures come as Macau is proposing changes to its anti-money laundering laws which will strengthen current regulations. The gaming authority is also conducting additional audits on the lucrative VIP gambling sector and more vetting of individual junket operators. (Reporting by Farah Master; additional reporting by Katy Wong; Editing by Miral Fahmy, Robert Birsel)