Some individual markets suffered bigger declines. Corn had its sharpest weekly tumble in 21 months.
Natural gas, gold and silver were among the few markets that rallied, helping the 19-commodity Thomson Reuters-Jefferies CRB index recover from a near nine-month low hit earlier in the session.
But for the week, the CRB, a globally watched commodities indicator, was down 2.8 percent after a rout in the past four sessions. That made for the index's worst weekly showing since late October.
"On balance, I think the down move we are seeing in commodities will continue into next week," said Edward Meir, analyst at INTL FCStone in New York.
Oil's benchmark Brent crude in London fell nearly 2 percent, trading below $105 a barrel by 2:45 p.m. EDT (1800 GMT) after plumbing a July low of $103.62.
US crude settled down 0.6 percent at $92.70 a barrel. For the week, it fell almost 5 percent for its biggest weekly loss since September.
Friday's slump in oil and metals came after data from the US Labor Department showed American employers hired at the slowest pace in nine months in March. A Reuters survey had earlier predicted moderate jobs growth for the month.
Concerns had already been growing about the outlook for the US economic recovery after weaker-than-expected numbers earlier this week on factory growth and private-sector hiring. The jobs data came as a further sign that Washington's austerity drive since December may be stealing momentum from the economy.
John Kilduff, partner at Again Capital, an energy hedge fund in New York, called the jobs report "a real disappointment".
"The recent decline in crude oil prices seemed to foreshadow this negative data point and the outlook for energy demand growth will be impaired as a result," Kilduff said.
Front-month corn on the Chicago Board of Trade was down slightly at $6.29 per bushel, recovering from a session low of $6.26-1/2. For the week, the contract fell 9 percent for its biggest weekly drop since June 2011.
Three-month copper on the London Metal Exchange slid to a session low of $7,384 a tonne, before paring losses to close at $7,406 for a decline of 0.5 percent.
Barclays Capital, known for its typically bullish outlook on commodities, said the liquidation across metals markets that began in mid-February had extended to April with no end in sight.
"Neither macro nor fundamental trends have offered any persuasive reasons to counteract this price trend during this time period," it said in a note.
In natural gas, the front-month contract in New York rose 4 percent to a 20-month high of $4.135 per million British thermal units. It increased more than 2 percent on the week for a seventh straight week of gains.
The rally was underpinned by a bullish weekly storage report for US gas released on Thursday. Price expectations for gas had strengthened over the past seven weeks after chilly late-winter weather helped whittle down inventories standing at record highs at the start of winter.
In gold, the most-active futures contract in New York, June , rallied over 1.5 percent at $1,575.90 an ounce. It was the biggest one-day gain since November, sparked by expectations that the dismal US jobs situation will spur the Federal Reserve to continue its bullion-friendly bond purchases.
Sentiment toward gold was also helped by the dollar's decline against the euro and other major currencies on Friday.