Image copyright AP Image caption Sandy Phan-Gillis was detained while trying to travel to Macau

An American woman held in China since last year has been charged with espionage, according to China's foreign ministry.

Sandy Phan-Gillis, 56, was first detained in March 2015 while in China as part of a US trade delegation.

Her husband, Jeff Gillis, said the charges were "absolutely false" and called for her release.

The news comes ahead of President Barack Obama's visit to China for a G20 summit in Hangzhou.

The president is scheduled to meet his Chinese counterpart Xi Jinping on Saturday amid heightened tensions between the US and China over Beijing's territorial claims in the South China Sea as well as cyber hacking.

Image copyright SaveSandy.org Image caption The delegation travelled across China, including Beijing and Shenzhen, a sister city of Houston

Ms Phan-Gillis, a Texan businesswoman who is of Chinese ancestry and is a naturalised US citizen, travelled to China to promote business opportunities in her hometown of Houston.

She was detained while trying to travel to Macau from the southern city of Zhuhai.

In June, a UN panel ruled that China had violated international human rights by denying her access to legal assistance and holding her without bringing her before judicial authorities.

A State Department official told Reuters the US remains "deeply concerned" about Ms Phan-Gillis and has "repeatedly pressed" Chinese authorities to provide more information on the case.

The US consulate in Guangzhou has provided consular assistance to Ms Phan-Gillis, which includes monthly visits, according to the State Department official.

Mr Gillis said his wife was accused of travelling to China on a spy mission in 1996, but her passport shows that she did not make a trip to the country during that period of time.

Ms Phan-Gillis has denied any wrongdoing and said her detention was political and not criminal, according to a letter transcribed by a US consular official in China.