HOUSTON, March 24 (Xinhua) --The number of active drilling rigs in the United States increased to 758 this week, up by four from the previous week and by 88 from this time last year, according to the weekly data released by Houston-based oilfield services company Baker Hughes on Friday.

These active drilling rigs included 593 oil rigs operating in U.S. oil fields, up by four from the previous week; 162 gas rigs, unchanged from last week; and three miscellaneous rigs, also the same as last week.

The rigs included 739 land drilling rigs, one inland water drilling rigs, and 18 offshore drilling rigs.

Of them, 50 were directional drilling rigs, 692 were horizontal drilling rigs and 16 were vertical drilling rigs.

So far, the Permian Basin in western Texas and eastern New Mexico has been the largest source of shale oil production growth in the United States, having become an engine of supply growth outside the Organization of the Petroleum Exporting Countries in the past years.