LONDON - The European Union's securities watchdog has begun preparations for increased scrutiny of crypto transactions after the bloc agreed groundbreaking rules to regulate what it called a "Wild West" sector, a public tender document showed.

While cryptoasset firms will be licensed by national regulators in the 27-country bloc, the European Securities and Markets Authority (ESMA) will monitor the bigger players.

ESMA put out a public procurement request on Tuesday to suppliers of trading data on crypto transactions, including spot trades and derivatives.

It excludes transactions from blockchain or the distributed ledger technology which underpins cryptocurrencies like bitcoin.

"The coverage should encompass all major exchanges and crypto assets so that it provides a fair representation of the crypto market landscape," ESMA said in its notice.

Regulators use transactions data to spot abuses in markets, find out who is on each side of a transaction, and look for risky build ups of positions which could undermine orderly markets.

"Data should be available with daily frequency and include access to order books where to see spreads and liquidity across exchanges and trading pairs (in fiat and crypto)," it said.

The contract is worth a maximum of 100,000 euros.

(Reporting by Huw Jones; Editing by Kim Coghill)