* Treasury sold $29 billion in seven-year notes, demand strong
Tensions in Ukraine, Venezuela fuel safety buying
* Fed bought $3.79 billion in Treasuries maturing in 2018
By Marina Lopes
NEW YORK, Feb 27 (Reuters) - U.S. Treasury debt prices rose on Thursday as tensions between Ukraine and Russia spurred safety buying, helping to stoke strong demand at a seven-year note auction.
The Treasury sold $29 billion in seven-year-notes at the auction, the final sale of the week. Yields ended slightly lower than where they were before the sale.
"There seems to be a lot of demand shown in the auctions all week and in particular today," said Lou Brien, a market strategist at DRW Trading in New York.
"That might indicate some international demand from Japan or China, but there has also been a bid because of international news on Ukraine and Venezuela, as investors look to park money," said Brien.
Tensions over Ukraine grew overnight, with Russia's Defense Ministry quoted as saying fighter jets along its western borders have been put on alert a day after it called a snap military exercise of 150,000 troops.
Other data showed an unexpected increase in the number of Americans filing new applications for unemployment benefits last week, which also boosted Treasury prices.
"The data has been weak, and although that has not bothered the stock market at all, the Treasury market has noticed and that has been part of the bid," said Brien.
Remarks by Federal Reserve Chair Janet Yellen during her testimony before the Senate Banking Committee provided little clarity on the impact of a harsh winter on recent economic weakness and did not stir prices.
Benchmark 10-year notes were up 6/32 in price, sending yields down to 2.653 percent, the lowest since Feb. 7. Thirty-year bonds were up 13/32, pushing yields down to 3.614 percent from Wednesday's close of 3.635 percent.
The Fed bought $3.79 billion in Treasuries maturing in 2018. It will buy $1 billion to $1.25 billion in Treasuries maturing between 2036 and 2044 on Friday, as part of its ongoing bond-buying program.
Investors await GDP data on Friday for further indications of the strength of the U.S. economy.