* Tensions in Ukraine push yen, Swiss franc higher
* Dollar index lower as weak U.S. economic numbers weigh
* Focus on Fed next week
(Recasts, updates prices, adds comment, details)
NEW YORK, Aug 15 (Reuters) - The dollar fell on Friday, hurt by generally weak U.S. economic data this week and heightened tensions in Ukraine that pushed Treasury yields lower.
Investors sold the greenback against the safe-haven yen and Swiss franc.
The Japanese and Swiss currencies advanced against most currencies after the government in Kiev said its artillery partially destroyed a Russian column in fighting overnight. Russia denied its forces had crossed into Ukraine, calling the Ukrainian report "some kind of fantasy.
The Swiss franc hit a 19-month high against the euro and a three-week peak versus the dollar. The yen, meanwhile, reversed losses against the dollar, turning higher.
"Risk has evaporated from the markets after the Ukraine headlines," said Omer Esiner, chief market analyst at Commonwealth Foreign Exchange in Washington. "We have seen investors use the yen and Swiss franc as safe harbors."
The yen and Swiss franc tend to benefit in times of global tension because of their deep liquidity. The dollar is also a safe haven, but recently investors have bought the greenback against emerging market currencies in periods of financial or geopolitical stress.
U.S. bond yields fell sharply on concerns about the Russia-Ukraine conflict, a negative for the dollar. Benchmark U.S. 10-year note yields fell to their lowest since June 2013. They were last at 2.35 percent, from 2.40 percent in the previous session.
In late trading, the dollar was down 0.1 percent against the yen at 102.33 yen after hitting a more than one-week high earlier in the session.
The euro, meanwhile, tumbled versus the Swiss franc to its lowest since January 2013. It was last at 1.2093 francs , down 0.2 percent. The dollar also fell versus the franc to a three-week trough. It last traded at 0.9028 franc , down 0.4 percent.
The U.S. currency slid versus the euro as well, with the latter up 0.2 percent to $1.3393.
The greenback's broad losses pushed the dollar index down 0.2 percent to 81.44.
Soft U.S. economic numbers for most of this week - including retail sales, jobless claims and a lower consumer sentiment index - have weighed on the dollar.
"The weak numbers were seen keeping the Fed on a low rate path for the foreseeable future," said Joe Manimbo, senior market analyst at Western Union Business Solutions in Washington.
Federal Reserve events should be the focus next week and could drive movements in currencies. Minutes from the Fed's late July meeting are due next Wednesday, followed by Thursday's start of a three-day central bankers' conference hosted by the Fed in Jackson Hole, Wyoming.
(Reporting by Gertrude Chavez-Dreyfuss; Editing by Meredith Mazzilli and Dan Grebler)