FRANKFURT (Reuters) - Germany's Volkswagen said its operating profit jumped 28 percent in the first quarter, helped by improved earnings at its core VW brand.

Operating profit came to 4.4 billion euros ($4.7 billion) in the three months through March, the carmaker said on Tuesday, compared with 3.44 billion it reported for the year-earlier period.

It said it still expected to report a full-year return on sales between 6 and 7 percent this year.

($1 = 0.9359 euros)

(Reporting by Maria Sheahan; editing by Harro ten Wolde)