LONDON (Reuters) - London-based fund manager Henderson Group (>> Henderson Group Plc) said on Thursday that third-quarter assets under management rose 6 percent, buoyed by positive market moves and currency gains after a slide in the value of sterling.

However the firm - which agreed earlier in October to buy U.S. rival Janus Capital (>> Janus Capital Group Inc) to create a firm with $6 billion in assets - said it had seen retail investors pull just over 1 billion pounds from its funds.

While that was partially offset by net inflows of 400 million pounds from its larger institutional clients, it still posted net outflows of just over 600 million pounds.

The long-term investment performance of its funds remained strong, it said in a statement, with 77 percent of funds outperforming over three years.

"This quarter's retail outflows were concentrated in the period immediately after the UK Referendum," said Andrew Formica, Chief Executive of Henderson, adding its pipeline of institutional business in the fourth quarter was strong.

Formica also said he was pleased with investors' support for the firm's merger with Janus.

(Reporting by Simon Jessop; Editing by Rachel Armstrong)

Stocks treated in this article : Janus Capital Group Inc, Henderson Group Plc