China's direct investment in the United States showed strong momentum in the first three months of this year despite a weak fourth quarter of 2012 and the negative impact of "national security" concerns on some deals.

During the first quarter, Chinese companies concluded eight mergers or acquisitions and nine greenfield investments - those involving construction of factories or offices - worth a total of $2.2 billion, according to a report released on Tuesday by Rhodium Group, a New York firm that tracks Chinese investment in the US.

M&A highlights were the acquisition by China National Offshore Oil Corp, or CNOOC, of the US drilling operations of Canada's Nexen Inc; auto-parts company Wanxiang Group's successful $257 million bankruptcy-auction bid for electric-battery maker A123 Systems Inc; BGI-Shenzhen's purchase of California-based Complete Genomics Inc; Hanergy Holding Group's purchase of solar technology company MiaSole; and Shanghai Fosun Pharmaceutical Co's stake purchase in Saladax Biomedical Inc.