Carlos said the Filipino sailors, using a long-range camera on Thitu island, spotted the debris drifting in strong waves near a sandbar about 800 yards (540 meters) off shore. They set out on a boat and retrieved the floating object and started to tow it back to the island.
As they were traveling back to the island, “they noticed that a China coast guard vessel with bow number 5203 was approaching their location and subsequently blocked their pre-plotted course twice,” Carlos said in a statement.
The Chinese coast guard vessel then deployed an inflatable boat with personnel who “forcefully retrieved said floating object by cutting the towing line" attached to the Filipino sailors’ rubber boat. The sailors decided to return to their island, Carlos said, without detailing what happened.
Maj. Cherryl Tindog, spokesperson of the military's Western Command, said the floating metal object appeared similar to a number of other pieces of Chinese rocket debris recently found in Philippine waters. She added that the Filipino sailors did not resist the seizure.
“We practice maximum tolerance in such a situation,” Tindog told reporters. “Since it involved an unidentified object and not a matter of life and death, our team just decided to return.”
In Beijing, China's Foreign Ministry denied that the debris was seized forcibly.
“The Philippine side salvaged and towed the object first. After friendly consultation at the site, the Philippine side returned the object to China, and China expressed appreciation for that,” ministry spokeswoman Mao Ning said. “There was no such thing as interception or forcible seizure at the scene.”
Metal debris from Chinese rocket launches, some showing part of what appeared to be a Chinese flag, has been found in Philippine waters in at least three other instances.
Rockets launched from the Wenchang Space Launch Center on China's Hainan island in recent months have carried construction materials and supplies for China's crewed space station.
China has been criticized previously for allowing rocket stages to fall to Earth uncontrolled. The Philippine Space Agency earlier this month pressed for the Philippines to ratify U.N. treaties providing a basis for compensation for harm from other nations' space debris, and NASA accused Beijing last year of “failing to meet responsible standards regarding their space debris” after parts of a Chinese rocket landed in the Indian Ocean.
The Philippine government has filed many diplomatic protests against China over aggressive actions in the South China Sea but it did not immediately say what action it would take following Sunday's incident. The Department of Foreign Affairs in Manila would usually wait for an official investigation report before lodging a protest.
Thitu island, which Filipinos call Pag-asa, hosts a fishing community and Filipino forces and lies near Subi, one of seven disputed reefs in the offshore region that China has turned into missile-protected islands, including three with runways, which U.S. security officials say now resemble forward military bases.
The Philippines and other smaller claimant nations in the disputed region, backed by the United States and other Western countries, have strongly protested and raised alarm over China’s increasingly aggressive actions in the busy waterway.
U.S. Vice President Kamala Harris, who is visiting Manila, was scheduled to fly to the western province of Palawan, which faces the South China Sea, on Tuesday to underscore American support to the Philippines and renew the U.S. commitment to defend its longtime treaty ally if Filipino forces, ships and aircraft come under attack in the disputed waters.