* New home prices fall at fastest pace on-month since Nov 2021

* New home prices fall at fastest pace on-year since Aug 2015

* Property sales fall for the 13th month in a row (Adds analysts' comments and details)

By Liangping Gao and Ryan Woo

BEIJING, Sept 16 (Reuters) - Woes in China's property market worsened in August, with official data showing home prices, sales and investment all falling in August, as a mortgage boycott and developers' financial strains further hurt confidence in the sector.

New home prices resumed their month-on-month decline in August, down 0.3%, Reuters calculations based on National Bureau of Statistics (NBS) data showed, dragged down by weak demand in smaller cities amid persistently slow deliveries by heavily-indebted developers. Prices were unchanged in June and July.

More significantly, prices extended their year-on-year contraction for the fourth month in August, with prices last month falling 1.3%, the fastest annual pace in seven years, and suggesting longer-term homebuyer aversion.

The deepening property woes are weighing on the outlook for the world's second-largest economy, which narrowly escaped a contraction in the second quarter. The sector, once a key driver of economic growth, has lurched from crisis to crisis since 2020 after regulators stepped in to cut excess debt at developers.

"The sector is still in the process of finding its bottom, though it is getting closer, even as policies have been eased across the board," said Zhang Dawei, chief analyst at property agency Centaline.

Authorities have taken steps to prop up the sector this year, including relaxations on home purchases, smaller downpayments, cuts in mortgage interest rates, and a bigger reduction in the selling price of homes.

Zhang said he expected Chinese authorities to roll out more measures in tier-one cities such as Beijing and Shanghai and tier-two cities to stabilise the market and restore buyers' confidence in the near term.

Confidence in the sector has been dampened by a mortgage boycott across the country since late June as developers stopped building presold housing projects due to strapped liquidity and strict COVID restrictions.

Separate data from the statistics bureau on Friday showed property sales declining for a 13th consecutive month in August, not helping to shore up sentiment.

Property sales by floor area dropped 22.58% year-on-year, according to Reuters calculations based on the NBS data, the sixth month in a row it suffered double-digit falls. Sales tumbled 23.0% year-on-year in the January-August period.