The roll-out of new rules today that aim to make European Union financial markets safer and more transparent has been glitch-free so far, though disruptions cannot be ruled out, the EU's markets watchdog said.

The new regime shines a spotlight on the inner workings of stock, bond, commodity and derivatives markets by forcing banks, asset managers and traders to provide detailed information on trillions of euro in transactions.

Big banks spent an estimated $2 billion collectively last year to upgrade IT systems to prepare.

"What we can see for our part, is no glitches so far," Steven Maijoor, chairman of the European Securities and Markets Authority (ESMA), told reporters.

"It will be the first time we have a complete overview of all financial instruments in the EU."

European stock and bond volumes were light in early trading.

"So far [there is] no difference compared to a regular day," said Markus Huber, a trader at City of London Markets.

"Volume isn't expected to be massive or back to normal either due to not everybody being back from holidays, and not much going on in regard to major news or economic data."

Fixed income volumes were lower at 1000 GMT compared with their average at that time over the previous 30 days, according to data provider Trax, a subsidiary of MarketAxess that tracks around 65 percent of all secondary market bond deals.

Sterling corporate bond volumes were 46% lower than their 30-day average, with euro sovereign bond volumes 24% lower and sterling sovereign bond volumes 11% lower.

Euro corporate bond volumes were 2% higher, according to Trax.

The new rules, known as Markets in Financial Instruments Directive II (MiFID II), were delayed by a year to give banks, asset managers and exchanges more time to get ready.

Harps Sidhu, head of capital markets at consultants KPMG, said it would become clearer by the end of the week if transaction reporting was working properly.

"The key thing to realise is MiFID II isn’t done. People are at various stages of readiness, which I think everyone accepts," Sidhu said.

Market nerves were eased by ESMA announcing measures just before Christmas to give companies more time to comply with some key requirements.

Regulators have said they will not crack down on poor compliance initially, as long as market participants show they are doing everything they can to get up to speed.

Maijoor said given the complexity and size of the reform, ESMA glitches could not be ruled out in coming days or weeks.