Wall Street had opened the session lower after North Korea announced it had set off an atomic weapon underground. Reports that OPEC was near announcing its first output cut in two years sent oil prices higher. But stock prices turned mixed by midday and were higher by early afternoon.

"We are heartened by the fact the market seems to be shrugging off a major geopolitical event," said Jim Russell, director of core equity strategy for Fifth-Third Asset Management in Cincinnati, which manages $22 billion.

But Russell added that because of the Columbus Day holiday, volume was too light to say the day's trading represented a trend or theme.

According to preliminary calculations, the Dow Jones industrial average rose 7.60, or 0.06 percent, to 11,857.81. The Dow remains near its record closing high of 11,866.69.

Broader stock indicators ended slightly higher. The Standard & Poor's 500 index rose 1.08, or 0.08 percent, to 1,350.66, and the Nasdaq composite index rose 11.78, or 0.51 percent, to 2,311.77.

The Dow briefly crossed 11,872.94, a new intraday trading high during the session. Last week the Dow Jones industrial average hit new closing records for three straight sessions. Stocks have been rallying since their six-month lows in late July; the Standard & Poor's 500 has rebounded more than 9 percent since its July lows.

Some cyclical stocks, such as semiconductors and department stores, have seen run-ups greater than 18 percent since the July lows, said David Sowerby, portfolio manager at Loomis, Sayles & Co, which manages $75 billion.

The rally has left investors divided about whether stocks are set to march higher or whether they are already at the top. With earnings season set to begin this week, investors will be watching closely for any disappointments.

Sowerby said he felt the market has room to go higher. "I just view these natural pauses as a buying opportunity," he said.

Equities volume was light and the U.S. bond market was closed for Columbus Day. Ten-year Treasuries closed Friday with a yield of 4.70 percent.

The U.S. dollar was mostly higher against other major currencies. Gold prices rose. A barrel of light crude settled at $59.96, up 20 cents, on the New York Mercantile Exchange.

In company news, the family that controls Cablevision Systems Corp. offered to take the company private for $27 a share in a deal that values the cable television operator at $7.9 billion. Cablevision rose $2.57 to $26.50.

Google Inc. rose $8.50 to $429 on reports by The New York Times and The Wall Street Journal that the company would announce a deal to acquire YouTube.com, the privately held video-sharing Web site, for roughly $1.6 billion. The deal was announced after today's closing bell and Google shares climbed $9.02, or 2.1 per cent, to $429.57 in after-hours trading on the Nasdaq Stock Market

Mercantile Bankshares Corp. rose $8.16 to $44.94 after PNC Financial Services Group Inc. agreed to buy the Mid-Atlantic bank for nearly $6 billion in a stock and cash deal. PNC fell $3.20 to $70.40.

Advancing issues led decliners by roughly 3 to 2 on the New York Stock Exchange, where consolidated volume came to 2.00 billion shares, down from 2.56 billion at the same time Friday.

The Russell 2000 index of smaller companies rose 4.76, or 0.64 percent, to 744.57.

Overseas, South Korea's benchmark Korea Composite Stock Price Index, or Kospi, dropped as much as 3.6 percent before closing down 2.4 percent to 1,319.40. Analysts warned that more selling could be ahead in South Korea, depending on the global reaction to the weapon test.

Chinese shares surged to five-year highs in anticipation of a strong stock-market debut by China's biggest lender, Industrial & Commercial Bank of China, later this month.