Amazon.com Inc shares hit another record on Thursday after e-commerce firm ChannelAdvisor Corp released strong online sales data.. ChannelAdvisor reported that client sales on Amazon.com jumped 30.6 per cent in June, compared with the same month last year. That year-on-year growth rate was up from May's rate of 25.8 per cent.. ChannelAdvisor also reported that client sales on eBay's online marketplace rose 17.7 per cent in June, compared with a year earlier. May's growth was 16 per cent on year.. ChannelAdvisor helps merchants sell more on websites such as Amazon.com, eBay.com and Google Inc's shopping site. Investors watch the firm's data closely because it provides an early window into the performance of the leading US e-commerce companies.. The second quarter is typically one of the slowest periods for online shopping, falling after the winter holiday buying binge and before the back-to-school rush. However, the ChannelAdvisor data suggests that Amazon and eBay performed solidly at the end of the second quarter.. "Together, these data points show that in June, all e-commerce channels performed better than in May," ChannelAdvisor CEO Scot Wingo wrote in a blog on Thursday. In May, "overall retail sales were muted due to weather trends, which seem to have dissipated in June", he said.. Amazon shares rose 1.2 per cent to $295.72 in early trading on Thursday and touched a record $295.88 before that. On Wednesday, the stock had reached a high of $293.34.. EBay shares rose 1.3 per cent to $55.57 in morning action on Thursday.. EBay is an investor in ChannelAdvisor.. Copyright @ Thomson Reuters 2013