China has denied US allegations that two of its fighter jets intercepted an American “radiation-sniffing” plane earlier this week, saying that its aircraft were acting “in accordance with the law”.

“Related remarks from the US side are inconsistent with fact,” the Chinese defence ministry said in a statement posted to its website late on Friday.

“On 17 May, a US reconnaissance aircraft was carrying out an operation in airspace over the Chinese Yellow Sea (the northern part of the East China sea), and Chinese aircraft acted to identify and investigate in accordance with the law,” the statement said, calling the action “professional” and “safe”.

The US air force said in an earlier statement on Friday that its plane, a WC-135 Constant Phoenix, was conducting a “routine mission” in international airspace when it was intercepted by two Chinese Sukhoi SU-30 fighter aircrafts.

The WC-135 is a so-called “sniffer plane” designed to scan the atmosphere for signs of nuclear activity.

“The WC-135 was operating in accordance with international law. While we are still investigating the incident, initial reports from the US aircrew characterised the intercept as unprofessional,” the US air force said.

Mid-air interceptions occur routinely in international airspace, but the US military will often call out foreign pilots if it judges the manoeuvres to be risky or unprofessional.

Meanwhile, China urged the US to halt such reconnaissance exercises in order to prevent future incidents.

“The American military’s frequent reconnaissance operations are the root cause of security issues between the Chinese and US navy and air forces,” the Chinese defence ministry’s statement said.