China has claimed US high-altitude balloons have flown over its airspace more than 10 times over the past year.

Beijing has made the claim after Washington accused China of operating a fleet of surveillance balloons around the world.

The development comes a day after US jets shot down a fourth flying object that the Pentagon said flew near sensitive military sites and was a risk to civilian aircraft.

It was downed over Lake Huron in Michigan at 2.42pm local time on Sunday on President Joe Biden's orders.

The row started when a suspected Chinese spy balloon was shot down by the US off the coast of South Carolina earlier this month.

Ships were deployed in the water to mount the recovery operation.

'US balloons illegally enter airspace'

China's foreign ministry spokesman Wang Wenbin has given no details about the alleged US balloons today.

He did not explain how they had been dealt with, or whether they had government or military links.

He said at a daily briefing: "It is also common for US balloons to illegally enter the airspace of other countries.

[b]"Since last year, US high-altitude balloons have illegally flown over China's airspace more than 10 times without the approval of Chinese authorities."

The US should "first reflect on itself and change course, rather than smear and instigate a confrontation,"[/b] the Chinese spokesman added.

China said the balloon shot down by the US over South Carolina was an unmanned airship made for meteorological research that had been blown off course.

It has accused the US of overreacting by shooting it down and threatened to take unspecified action in response.

'Heightened alert' after latest 'objects'

US Secretary of State Antony Blinken cancelled a visit to Beijing following the sighting of the balloon earlier this month.

Many had hoped the visit would put the brakes on the sharp decline in US-China relations over Taiwan, trade, human rights and threatening Chinese actions in the disputed South China Sea.

The balloon was equipped to detect and collect intelligence signals as part of a huge, military-linked aerial surveillance programme that targeted more than 40 countries, the Biden administration declared on Thursday, citing imagery from American U-2 spy planes.

US Air Force general Glen VanHerck admitted he did not know what the last three objects were or how they stayed aloft before being shot down.

However, he told reporters they were not the same as the balloon which started the row.

"We're calling them objects, not balloons, for a reason," he said - also refusing to rule out any explanation when asked if they could be extra-terrestrial.

Part of the reason for the repeated shootdowns is a "heightened alert" following the alleged Chinese spy balloon, General VanHerck said.

The United States has placed economic restrictions on six Chinese entities it said are linked to Beijing's aerospace programmes as part of its response to the incident.

The US House of Representatives also voted unanimously to condemn China for a "brazen violation" of US sovereignty and efforts to "deceive the international community through false claims about its intelligence collection campaigns".

China defends use of laser in new incident

Wang Wenbin repeated China's dismissal of the US claims, saying: "The frequent firing of advanced missiles by the US to shoot down the objects is an over-reaction of over-exertion."

Meanwhile, on Monday the Philippines accused a Chinese coastguard ship of targeting a Filipino vessel with a military-grade laser and temporarily blinding some of its crew in the South China Sea, calling it a "blatant" violation of Manila's sovereign rights.

China said the Philippines coastguard ship had trespassed into Chinese waters without permission on 6 February and that China responded "professionally and with restraint".

China claims virtually all of the strategic waterway and has been steadily building up its maritime forces and island outposts.