* Swiss investigating "a number of" initial coin offerings
* Probe into whether Swiss laws violated
* This includes anti-money laundering rules
* Second clamp-down by Swiss in less than two weeks (Adds details from statement, background)
ZURICH, Sept 29 (Reuters) - Swiss financial watchdog FINMA said it is investigating a number of initial coin offerings (ICOs) over whether they violated Swiss laws including possible money laundering and "terrorist financing".
It is the second crackdown in less than two weeks by FINMA as it grapples with the booming but still opaque world of cryptocurrencies.
"FINMA has observed a marked increase in initial coin offerings conducted in Switzerland," it said in a statement on Friday.
Switzerland has played host to four out of the six largest ICOs to date. These include one by Tezos, a new blockchain platform, which in July raised the equivalent of $230-$240 million in bitcoin and ether, and one by Bancor Protocol, which enables people to create cryptocurrencies. It raised over $150 million in June.
Switzerland does not have rules governing conduct specifically for ICOs, which create and sell digital currencies or tokens to investors to finance start-up projects.
But depending on how an ICO is structured, some parts of the procedure may be covered by existing regulations, FINMA said.
It said it was particularly concerned that some ICOs may be in breach of regulations on "combating money laundering and terrorist financing", as well as laws on banking, securities trading and collective investment schemes.
Swiss ICOs have primarily been run by foundations based out of Zug, Switzerland's "Crypto Valley".
Earlier this month, the Crypto Valley Association -- of which Thomson Reuters is a member -- issued a statement in support of ICO regulation and said it had begun working with its members on developing an ICO code of conduct.
This month FINMA closed down what it said was the provider of a fake cryptocurrency and said it was investigating around a dozen other possible fraud cases.
The move came on the heels of Chinese authorities' ordering Beijing-based cryptocurrency exchanges to stop trading and immediately notify users of their closure.
Virtual currencies such as Bitcoin, which are issued and usually controlled by their developers and not backed by a central bank, are hailed by their supporters as a fast and efficient way of managing money.
But regulators and traditional banks are increasingly concerned about the risks of fraud in the burgeoning online cryptocurrency underworld.
JPMorgan Chief Executive Jamie Dimon said this month that Bitcoin, the original and still the biggest cryptocurrency, "is a fraud" and will eventually "blow up".
ICOs have fuelled a rapid ascent in the value of all cryptocurrencies, from about $17 billion at the start of the year to a record high of close to $180 billion at the beginning of September.
(To see a Reuters SPECIAL REPORT: Chaos and hackers stalk investors on cryptocurrency exchanges, click on) (Reporting by Michael Shields, Joshua Franklin and Brenna Hughes Neghaiwi; Editing by Susan Fenton)