(Reuters) - Betterment LLC, an automated financial adviser, suspended all trading on Friday morning as Britain's vote to quit the European Union sent a shock wave through global financial markets, The Wall Street Journal reported.

Clients were not aware of the halt, which ran from the market's 9:30 a.m. open until noon, the Journal said.

The company, which manages $4.8 billion, took the step to protect investors from paying the higher transaction costs associated with buying and selling securities during times of extreme market volatility, the WSJ said.

Betterment was not immediately available for comment.

Wall Street suffered its largest sell-off in 10 months on Friday after Britain's decision to leave the European Union caught traders wrong-footed.

(Reporting by Anya George Tharakan in Bengaluru; Editing by Leslie Adler)