ST. LOUIS (Reuters) - Standard Chartered Plc has hired two former prosecutors to police its transactions for criminal activity, a spokesman said on Friday, as the British bank wrestles with a series of legal and compliance problems.

The hires in the past two months coincide with a federal probe of Standard Chartered's past compliance with sanctions laws, the latest in a string of legal issues it has faced, including some with U.S. anti-money laundering laws.

In late November, Standard Chartered hired Vincent G. Heintz, a former assistant director of the enforcement and investigations division of U.S. audit watchdog Public Company Accounting Oversight Board (PCAOB), to lead its U.S. financial crimes compliance investigations unit, said bank spokesman Chris Teo.

This month, it hired former federal prosecutor Evan Weitz, an expert on U.S. money laundering law, to serve as Heintz's deputy, Teo added.

In 2012 the bank paid U.S. authorities, including New York state's banking regulator, $667 million over sanctions violations involving Iran and other countries.

In August of this year, the New York regulator fined Standard Chartered another $300 million after a monitor it appointed uncovered shortcomings in the automated monitoring systems the bank relies on to detect money laundering and other criminal activity.

Standard Chartered hired Heintz and Weitz to lead U.S. investigators probing transactions flagged by frontline employees and software systems to determine if the activity is truly suspicious – possibly linked to criminal activity – and therefore must be reported to authorities.

The two new hires will work in the bank's offices in New Jersey and Manhattan.

Heintz previously served as a prosecutor with the New York County District Attorney's Office where he combated organized crime, money laundering and terrorism finance.

Weitz, the recipient of several awards for his prosecution of financial institutions that violated the Bank Secrecy Act, the primary U.S. anti-money laundering law, is best known for his participation in the prosecution of HSBC.

HSBC in 2012 agreed to pay $1.9 billion for compliance lapses that led to violations of U.S. sanctions against Iran and allowed drug cartels to launder hundreds of millions of dollars.

That case prompted Congress to step-up pressure on regulators to better hold banks, and bankers, to account for compliance lapses.

(Reporting by Brett Wolf; Editing by Christian Plumb)