WASHINGTON 

China is ramping up its spying activities in Europe, NATO Secretary-General Jens Stoltenberg warned Wednesday as tensions worsen between Washington and Beijing over a suspected surveillance balloon. 

Stoltenberg said the aircraft's discovery over the continental US "confirms a pattern of Chinese behavior where we see that China over the last years has invested heavily in new military capabilities, including different types of surveillance and intelligence platforms."

"We're also seeing increased Chinese intelligence activities in Europe. Again, different platforms. They use satellites, they use cyber, and as we've seen over the United States, also balloons," he told reporters during a joint press conference with Secretary of State Antony Blinken.

"So we just have to be vigilant. We need to be aware of the constant risk of Chinese intelligence and then step up, what do we do to protect ourself, and we need also to react in a in a prudent, responsible and vigilant way," he added.

The US shot down the balloon on Saturday off the coast of South Carolina in US territorial waters after it had transited much of the country.

Beijing has admitted its ownership of the aircraft, but said it was used for meteorological research and calling Washington's decision to down it "unacceptable and irresponsible." 

The balloon's discovery prompted Blinken to call off a planned weekend visit to China, and postpone it until unspecified conditions are met.

Speaking alongside Stoltenberg, the US top diplomat said American teams are continuing work to salvage the debris, and are continuing to gather intelligence from the remnants, as well as what was observed during the balloon's transit.

"As to who was responsible for that, China is and it doesn't matter, on one level, which individuals may or may not have been responsible, the fact is, China engaged in this irresponsible action in violation of our sovereignty, and territorial integrity, and international law," he said.

Additional information on the balloon will be shared with the public "in the days ahead," Blinken added.