China's multi-billion-dollar National Social Security Fund has selected Citigroup and Northern Trust as its custodian banks for overseas investment, AFP reported. The NSSF, which as established to fund living and medical expenses for the elderly and the poor, secured approval in May to invest up to US$5.5 billion dollars, or 20% of the more than US$26.5 billion it has under management, the fund said in a statement on its website. Citigroup spokeswoman Marine Mao confirmed the selection of the US-based banking group. "It is only Northern Trust and Citigroup that have been selected," she said. Xiang Huaicheng, head of the national fund, said earlier that it would invest up to US$800 million overseas by the end of the 2006, mainly focusing on Hong Kong as well as US and European markets.