The world's two biggest auction houses had a strong start in sales for the year, reflecting the upward trending of the art market with major growth online and with new clients. Prices soared at the top, especially for contemporary art.

London-based Christie’s reported 12 percent growth in sales reaching $4.6 billion, and New York-based Sotheby’s did $3.1 billion in art sales in the first half of the year, up 22 percent, and will announce a consolidated sales report in August.

Among Christie's top performers was “Black Fire I” (1961) by Barnett Newman, which sold for an artist record of $84.16 million, and was one of 51 works bringing over $10 million each in the first half of the year. Christie's May evening sale in New York brought an auction industry record of $744.9 million. 

Fresh clients represented 24 percent of all buyers. Asians constituted 20 percent of new buyers at Christie's which expanded facilities in Asia. 

Online sales surged 71 percent from the first half of 2013, according to Christie's, which spent $50 million in three years on its online platform. Its top online auction price was $905,000 for a Richard Serra. 

Sotheby’s  hits included Monet’s “Nympheas” for $54 million, and in April, John James Audubon's "Birds of America" sold for an online auction record of $3.5 million.