Google on Thursday rolled out search engine refinements as Microsoft strives to lure people to Bing and Twitter heightens appetites for real-time updates and news.

Google modifications include tools that let people limit online searches to only serve up results from the past hour, or by specific date ranges.

"This can be particularly helpful when you're looking for the freshest information," Google engineer Patrick Riley and product manager Nundu Janakiram said in a blog post.

"Or, if you have some idea of when the information you're looking for may have been published to the Web."

Google users can choose to be shown search only results from blogs, news, or Web pages that they have visited or those they haven't visited.

"This can be particularly helpful when you're researching something you've already explored and you want to return right where you left off," Riley and Janakiram said.

"To use this option you'll need to be signed in to your Google Account and have Web History enabled."

A new tool also modifies searches to include more or fewer shopping websites depending on how interested people are in commercial pitches online.

Google put the features in a Search Options side panel it added to search results pages in May. To access the new tools, one clicks on a "show options" link displayed above search results.

The Bing search engine Microsoft launched in May was designed to intuitively understand what people are seeking on the Internet and challenge online king Google.

The US software colossus described Bing as a "Decision Engine" aimed at online shoppers trying to make buying decisions, plan trips, research health matters, or find local businesses.

Bing posted a slight increase in its share of the US search market in August, the third month in a row of modest gains, according to online tracking firm comScore.

Bing increased its market share to 9.3 percent in August from 8.9 percent in July and 8.4 percent in June, comScore said.

Google remained the overwhelming leader of the lucrative US search and advertising market in August with a 64.6 percent market share, a dip of 0.1 percent from July. Yahoo!'s share was unchanged at 19.3 percent in August.

Yahoo! and Microsoft, after months of negotiations, unveiled a 10-year Web search and advertising partnership in late July that set the stage for a joint offensive against Google.

Under the agreement, Yahoo! will use Microsoft's search engine on its own sites while Yahoo! will provide the exclusive global sales force for premium advertisers.

Microsoft is integrating messages from prominent users of wildly popular micro-blogging service Twitter into results generated by Bing.

Twitter is seen by some technology analysts as the next frontier in the field of Web search because of the real-time nature of the messages from its users.

Twitter's real-time stream of messages of 140-character-or-less is not currently searchable on Google.

Microsoft said its efforts with Bing and Twitter were "an initial foray into integrating more real time data into our search results."