Google retained its lead of the US search engine market in June, when it handled almost half of all queries, leaving Yahoo, Microsoft and others to fight for the remaining usage share, Nielsen/NetRatings said on Friday.

Google processed almost 2.67 billion queries, or 49.4 per cent of June's total, while Yahoo followed in a distant second place with 1.24 billion, for a 23 per cent market share.

Microsoft's MSN unit (10.3 per cent), Time Warner's AOL (6.9 per cent) and IAC/InterActiveCorp's (2.3 per cent) rounded out the top five.

In terms of usage growth, led the pack with 66 per cent more queries than in June 2005, followed by Google (31 per cent) and Yahoo (29 per cent.) MSN and AOL had growth below 4 per cent each.

Online ads delivered along with search engine results have become a multibillion dollar market in recent years, almost single-handedly fueling Google's impressive revenue growth and stratospheric stock price.

Drawn by the revenue opportunity, Yahoo, Microsoft, AOL and have all invested heavily in their search engine services and search-based ad offerings.