By Sam Forgione

NEW YORK (Reuters) - Investors in U.S.-based mutual funds pulled $1.3 billion out of bond funds in the week ended April 1 as tax deadlines approached for retail investors, data from the Investment Company Institute showed on Wednesday.

The outflows were the first in 12 weeks, or since early January, according to the data from ICI, a U.S. mutual fund trade organization. The withdrawals came ahead of the April 15 tax filing deadline.

Stock funds posted $1.6 billion in total outflows in a second straight week of withdrawals and their biggest since early January. Funds that specialize in U.S. stocks posted $3.3 billion in outflows, for a fifth straight week of withdrawals, though they were less than the prior week's $4.5 billion in withdrawals.

Withdrawals from U.S.-focused stock funds again accounted for the total outflows from stock funds. Funds that specialize in international shares attracted $1.8 billion in a 13th straight week of inflows. The inflows were the lowest in six weeks.

"We are moving towards the tax deadline, whereby there is a tendency for people to liquidate some assets in order to pay their taxes due," said Robbert van Batenburg, director of market strategy at brokerage Newedge USA LLC in New York.

He said the tax season also may have contributed to outflows from U.S.-focused stock funds, while the European Central Bank's recently launched bond-buying stimulus program likely spurred inflows into foreign-focused stock funds.

The benchmark S&P 500 stock index fell 0.1 percent over the period while the Barclays U.S. Treasury Index gained 0.3 percent.

Hybrid funds, which can invest in stocks and fixed income securities, attracted $720 million for a 12th straight week of inflows.

(Reporting by Sam Forgione; Editing by Leslie Adler)