The Ogilvy Group China announced in a statement today it has agreed to acquire Black Arc Advertising, the country's leading agency specializing in real estate-related advertising and promotions. The multinational advertising firm plans to target at the fast growing property-related advertising market. Expenditure was estimated to have reached approximately 1 billion US dollars in 2005.    ''The property sector is one of the fastest-growing and most important in the Chinese economy. Our investment in Black Arc Advertising puts Ogilvy at the forefront of the property marketing space and allows us to participate in the significant marketing opportunities being created in this area,'' said TB Song, Chairman of Ogilvy & Mather Greater China. Established in 1996, Black Arc is one of the best-known property- specialist agencies in China, focusing on building corporate property brands. Headquartered in Shenzhen, Black Arc has built up an unmatched national network with offices in the major Chinese cities of Beijing, Hangzhou, Chengdu and Chongqing. The agency plans to open a Shanghai office later in 2007. Clients include China's largest national property developers such as China Vanke Co., China OCT, Zhong Hai, Sunco China, and China Merchants.