U.S. energy firms this week added oil and natural gas rigs for a fourth week in a row to the highest level since June, energy services firm Baker Hughes said in its closely followed report on Friday. The oil and gas rig count, an early indicator of future output, rose by four to 592 in the week to February 21. Despite this week's rig increase, Baker Hughes said the total count was still down 34, or 5% below this time last year. Baker Hughes said oil rigs rose by seven to 488 this week, their highest since September, while gas rigs fell by two to 99.