SHANGHAI/HONG KONG (Reuters) - Chinese brokerage Haitong Securities Ltd (>> HAITONG Securities Company Limited)<6837.HK> is in talks to buy Portuguese bank Banco Espirito Santo's (BES) investment banking unit as Chinese finance firms snap up more overseas assets to try to offset slowing growth at home.

A purchase of the bailed-out Portuguese lender's unit would be Haitong's first acquisition outside China and Hong Kong as Chinese financial companies scoop up assets of Western banks hammered by bad debts.

It would be the highest-profile overseas deal by a Chinese brokerage since Citic Securities (>> CITIC Securities Company Limited) Citic, China's largest brokerage, purchased CLSA from French bank Credit Agricole SA for $1.25 billion (796.72 million pounds) in 2013.

Haitong said in a statement late on Thursday it's in talks to buy Banco Espirito Santo de Investimento SA (BESI), BES's investment banking arm, confirming an earlier Reuters story.

A person with direct knowledge of the matter earlier declined to disclose how much Haitong might pay for the business. The person declined to be identified as the talks were not public at the time.

Local media in Portugal have valued BESI at around 400 million euros (314 million).

A spokesman for BESI did not offer any immediate comment when contacted by Reuters.

Portugal's central bank rescued BES using 4.9 billion euros of public funds in August this year and is now seeking to recoup those funds through asset sales.

BESI, the largest investment bank in Portugal, made a net profit of 3 million euros in the first half of 2014 while its parent BES made a net loss of 3.6 billion euros in the same period, according to the company's website. BESI employs about 1,000 people and had 5.8 billion euros in assets at the end of June 2014.

Haitong raised $1.7 billion through a Hong Kong share listing in 2012. It said in the prospectus for that deal it was setting aside about 35 percent of proceeds "for strategic acquisitions of overseas securities firms and/or further expansion of our overseas securities business."

In October last year China Construction Bank Corp bought Brazil's Banco Industrial e Comercial SA (>> Banco Industrial e Comercial SA), a mid-sized lender with a large portfolio of bad loans.

Industrial and Commercial Bank of China bought 80 percent of Standard Bank's Argentina SA from Standard Bank London Holdings PLC for an estimated $600 million in cash in 2011.

"It's been very rare to have the opportunity globally in the last five years to buy a controlling stake in any sizeable financial company, so it's an opportunistic buy," said Jim Antos, banking analyst at Mizuho Securities Asia.

Haitong shares were halted on Thursday ahead of the announcement. Haitong's shares have risen 44 percent so far this year in Shanghai, outpacing a 27 percent rise in the Shanghai CSI 300 index <.CSI300>.

(Additional reporting by Lawrence White and Elzio Barreto; Editing by Denny Thomas and Kenneth Maxwell)

By David Li and Vicky Bi