China may have conducted secret nuclear tests that potentially violated an international agreement, according to a U.S. State Department report. The Chinese government has refuted the accusations made by the U.S.

China may have secretly conducted underground low-yield nuclear tests in the northwest region of the country, according to a report from the Wall Street Journal. "Some compliance concerns are raised and some findings of violations are made," the State Department claimed.

"China's possible preparation to operate its Lop Nur test site year-round, its use of explosive containment chambers, extensive excavation activities at Lop Nur, and a lack of transparency on its nuclear testing activities ... raise concerns regarding its adherence to the zero yield standard," the report stated.

Nuclear test explosions are banned under the Comprehensive Test Ban Treaty. The CTBT allows countries to carry out testing and other activities to ensure the safety of nuclear weapons, but nuclear explosive reactions are prohibited.

China, which is estimated to have about 300 nuclear weapons, and the U.S. are two of the eight countries who have signed the 1996 accord. However, neither country has ratified it, so they aren't bound to the treaty and aren't obliged to allow inspections. The U.S. and China say they obey the terms of the nuclear agreement despite not ratifying it. Russia, France, and the United Kingdom have signed and ratified the CTBT.

The U.S. is suspicious that the Chinese government is testing nuclear weapons because, in recent years, there have been interruptions of data transmissions from monitoring stations in China that detect radioactive emissions and seismic activity.

A spokeswoman for the CTBT organization informed the Wall Street Journal that there had been no interruptions in data transmissions from China's five sensor stations since the end of August 2019, following an interruption that started in 2018.

The Chinese Communist Party denied the American allegations and called the accusations "a complete distortion of the facts."

"The U.S. neglects all the facts and makes wanton accusations against China. This is irresponsible and ill-intentioned," Chinese Foreign Ministry spokesman Zhao Lijian said on Thursday. "The U.S. criticism of China is entirely groundless, without foundation, and not worth refuting."

This charge against China follows a Fox News report that was released on Wednesday, alleging that the coronavirus originated from a virology lab in Wuhan, China.