China may have conducted low level nuclear tests: US

In a statement that could fuel US-Chinese tensions, the US State Department has said in a report that China may have secretly conducted low-level underground nuclear tests despite claiming to observe an international pact banning such blasts.

The finding, first reported by The Wall Street Journal, may worsen ties already strained by US charges that the global Covid-19 pandemic resulted from Beijing's mishandling of a 2019 outbreak of the coronavirus in the city of Wuhan, South China Morning Post reported.

US concerns about Beijing's possible breaches of a 'zero yield' standard for tests have been prompted by activities at China's Lop Nur nuclear test site throughout 2019, the State Department report said on Wednesday.

Zero yield refers to a nuclear test in which there is no explosive chain reaction of the type ignited by the detonation of a nuclear warhead.

"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 said, without providing evidence of a low-yield test.

Beijing's lack of transparency included blocking data transmissions from sensors linked to a monitoring centre operated by the international agency that verifies compliance with a treaty banning nuclear test explosions.

The 1996 Comprehensive Test Ban Treaty (CTBT) allows activities designed to ensure the safety of nuclear weapons.