BEIJING, June 3 (Xinhua) -- China's insurance sector saw premium income drop 7.8 percent year on year to 1.7 trillion yuan (about 260 billion U.S. dollars) in the first four months of the year, according to official data.

The decline came as authorities enhanced regulation of the sector to defuse financial risks.

Property insurance firms posted a 16.1-percent increase, but life insurance companies registered a 13.6-percent dip, data from the China Banking and Insurance Regulatory Commission showed.

Premium income for life insurance started to pick up in March and April, up 6.1 percent and 9.9 percent year on year, respectively.

Online insurance business continued to expand. Online-only insurers saw their premium income up 85 percent year on year to 4.5 billion yuan.

Outstanding investment by insurers reached 15.4 trillion yuan as of the end of April, up 3.2 percent from the start of the year, with a yield of 1.57 percent in the January-April period, according to the commission.

Total assets of the insurance industry stood at 17.3 trillion yuan at the end of April, representing an increase of 3.6 percent from the beginning of the year.