Brazil's economy contracted 0.18 percent in May, compared to the previous month, marking its worst performance of the year, the Central Bank said Thursday.

The Central Bank's Index of Economic Activity, or IBC-Br, fell in May for the second time this year.

The index dropped 0.09 percent in February and registered tepid growth of 0.05 percent in March and 0.12 percent in April.

The IBC-Br index is used as a preview of the gross domestic product number, which is released quarterly, but the Central Bank indicator is not as broad and tends to overestimate economic growth on the upside.

The contraction in economic activity registered in May was the largest since December, when the index fell 1.37 percent.

Brazil's economy, according to Central Bank estimates, contracted 0.17 percent in May, compared to the same month in 2013, on a seasonally unadjusted basis.

The gross domestic product grew 0.58 percent in the January-May period, compared to the same period in 2013, and increased 1.93 percent on a year-on-year basis in May.

The figures confirm that Brazil's economy is slowing, a trend highlighted by economic indicators, including industrial production, in recent months.

Private bank economists have revised their GDP forecasts downward for seven straight weeks and now expect the economy to grow just 1.05 percent this year.

The government is forecasting economic growth of about 2 percent for this year, while the Central Bank recently revised its estimate downward to 1.6 percent.

Brazil's GDP expanded by 7.5 percent in 2010, but the economy posted weak growth of 2.7 percent in 2011 and just 1 percent in 2012.

The South American country's economy grew 2.3 percent in 2013.