HONG KONG, April 30 (Reuters) - Cases of negative equity in Hong Kong's residential mortgage loans rose 27% in the first quarter from the previous one to the highest in 20 years, the city's de facto central bank said.

Hong Kong's private home prices have fallen for 10 consecutive months before edging up in March, after the financial city lifted curbs to boost the ailing property market.

Prices in one of the world's most expensive property markets dropped 1.8% in the January-March quarter, and were around 20% off their 2021 peak due to higher mortgage rates, an outflow of talent and a weak market outlook.

The Hong Kong Monetary Authority said in a statement on Tuesday its survey estimated 32,073 cases of negative equity at the end of March, the highest since the first quarter of 2004.

The cases involved HK$165.3 billion ($21.13 billion), compared with 25,163 cases and HK$131.3 billion at the end of December.

But mortgage delinquency ratio remained unchanged at 0.09%, it added. ($1 = 7.8216 Hong Kong dollars) (Reporting by Clare Jim; Editing by Ros Russell)