Renewed fighting in Ukraine rattled markets Friday. Reports that Ukrainian forces attacked Russian military vehicles that had crossed the border knocked stock markets down in the afternoon and sent traders into the safety of U.S. government bonds.

By the end of the day, the Standard & Poor’s 500-stock index was back to where it started as investors realized that a wider conflict was not underway.

John Canally, the chief economic strategist at LPL Financial, said it is understandable that traders dropped stocks in response to the flare-up. “Anyone who doesn’t want to lose their job over the weekend sells first and asks questions later,” he said.

Canally said he suspects the dispute between Russia and Ukraine will probably follow the pattern of recent months. Worrying headlines will be followed by soothing speeches. “We’ve been here before,” he said.

The S&P 500 fell 0.12 of a point to 1955.06. It ended the week with a gain of 1.2 percent. The Dow Jones industrial average fell 50.67, or 0.3 percent, to 16,662.91, while the Nasdaq composite gained 11.93 points, or 0.3 percent, to 4464.93

Mark Luschini, chief investment strategist at Janney Montgomery Scott, said that one reason world events seem to be driving trading recently is that there is a lack of anything else for traders to focus on. All but a handful of big companies have turned in second-quarter results, and no major economic reports came out this week.

“For the moment, geopolitical events seem to hold the interest of the few people at their desks in mid-August,” Luschini said.

The yield on the 10-year Treasury note plunged as low as 2.30 percent, the lowest since June 2013, as traders seeking safety shifted money into U.S. government bonds.

In late afternoon trading, the yield climbed back to 2.34 percent, still down from 2.40 percent late Thursday.

Monster Beverage soared 30 percent to $93.49 after Coca-Cola announced plans to pay $2 billion for a stake in the maker of caffeinated drinks.

Supervalu, a grocery store chain, said hackers gained access to its computer network for handling credit-card transactions. Supervalu fell 28 cents, or 3 percent, to $9.31.

— Associated Press