One of the business partners is Sino Life Insurance Co, according to Nomura Holdings Inc.

"The demand for repayment is surprising because Sino Life, Kaisa's second-largest shareholder, is the joint venture partner of one of the projects," said Annisa Lee, a credit strategist in Hong Kong at Nomura.

Joint ventures are usually based on the premise that both partners are going concerns, so one often has the ability to pull out if the other is falling behind on its finances, she said.

The demands for repayment are the latest setback for Kaisa after several key executives quit and authorities in Shenzhen blocked some of its projects. Chairman Kwok Ying Shing resigned last month, triggering the default on the HSBC loan.

Chief Financial Officer Cheung Hung Kwong and Vice-Chairman Tam Lai Ling also left.

Kaisa has projects in more than 30 cities including Shenzhen as well as neighboring Guangzhou and Dongguan, according to its website. Developments include large residential communities, high-end apartments and industrial parks.

The company had a total land bank of approximately 23.6 million square meters as of June 30, sufficient for the group's development needs for the next five years, according to its interim report last year.