* 5 banks, 10 insurers, 12-plus fund firms move/bolster ops
* 139 banks from 28 countries based in Duchy
* Government agency sees more following in 2018 (Adds detail from statement, bullet points)
LONDON, March 1 (Reuters) - More than 20 major international institutions chose to set up all or part of their activities in Luxembourg last year, the country's financial development agency said on Thursday, linking the decisions to Britain's move to leave the European Union.
The tiny EU-member state is one of several countries vying for a slice of Britain's lucrative financial services sector as slow progress in its talks to exit the bloc prompts firms to move ahead with contingency plans to secure EU market access.
During 2017, five banks including Citibank, JP Morgan and China Everbright; more than a dozen global asset managers including Blackstone and Carlyle; and 10 global insurance companies decided to establish or expand their presence in the duchy, Luxembourg For Finance said in a statement.
"Following the United Kingdoms decision to leave the European Union, last year alone over twenty top-ranked international institutions chose Luxembourg to set up all or part of their activities and benefit from the specialisation that exists within the Luxembourg financial ecosystem," it said in a statement.
A total of 139 banks from 28 countries are based in Luxembourg, it added, with a focus on investment management, private banking, and the business and trade finance sectors.
"Luxembourg is expecting further announcements from businesses over the coming months, whether in the insurance, fund management, banking or fintech sectors," it said. (Reporting by Simon Jessop Editing by Silvia Aloisi and Mark Potter)