Investors added U.S. Treasuries to their portfolios in the latest week after a surprisingly weak jobs report and jitters over the European debt crisis, a survey released on Tuesday showed.

The share of investors who said on Monday they were long, or holding more Treasuries than their portfolio benchmarks, rose to 4 percent from zero last week, J.P. Morgan Securities said on Tuesday.

Last week was the first time since February 2005 that there were no outright longs.

Worries over an economic slowdown and fears of contagion from the public debt problem in Europe have stoked safe-haven bids for Treasuries, overshadowing historically low yields on Treasuries and the risk of a U.S. default due to the protracted fiscal wrangling in Washington, analysts said.

Renewed interest in Treasuries could boost bidding for this week's $66 billion in longer-dated supply.

The U.S. Treasury Department will auction $32 billion in three-year notes on Tuesday; $21 billion in 10-year debt on Wednesday and $13 billion in 30-year bonds on Thursday.

According to the latest J.P. Morgan survey, the share of investors who were neutral, or owning Treasuries equal to benchmarks, fell to 72 percent from 75 percent the prior week.

The share of investors who said they were short U.S. government debt, or holding more Treasuries than their benchmarks, dipped to 24 percent from 25 percent.

This was the lowest level of outright shorts since May 2, bringing the net shorts -- the difference between shorts and longs -- to the lowest in four weeks, J.P. Morgan said.

In early Treasury trading, prices on benchmark 10-year Treasury notes were up 8/32 for a yield of 2.90 percent, down 3 basis points from late on Monday and down 22 basis points from a week earlier.

(Reporting by Richard Leong; Editing by James Dalgleish)