The IMACEC economic activity index, encompassing about 90 percent of the economy, tallied in gross domestic product figures, was boosted by sharp increases in mining and manufacturing, the bank said in a statement.
Mining growth in Chile, the world's top copper producer, jumped 8.6 percent on rising copper prices early in 2018, the data showed, while non-mining sectors grew 3.5 percent.
Overall monthly growth topped a Reuters forecast of 3.4 percent.
Compared with December, economic activity increased a seasonally adjusted 0.8 percent.
Last week, the Organization for Economic Co-operation and Development (OECD) said it expects Chile's economy to grow 2.9 percent in 2018 and 2019 as copper prices rebound and investment recovers gradually.