Insurance premiums in China rose 13 percent in the first half of the year from a year earlier to 306 billion, Reuters reported, citing China Insurance Regulatory Commission data released Tuesday.   The officials figures showed that premiums from life insurance rose 11.3 percent to 201 billion yuan; property insurance premiums rose 15.3 percent to 78 billion yuan; and health and casualty insurance jumped 19.6 percent to 27 billion yuan.   By the end of June, total assets of China-based insurance companies had reached 1.74 trillion yuan, up 215 billion yuan from the beginning of this year, the data showed.   China's fledgling insurance industry has been developing rapidly as Beijing dismantles a cradle-to-grave welfare system. Annual growth in the country's insurance premiums accelerated to 13.95 percent in 2005 from 11.3 percent in the previous year, Reuters said.