In a significant development, China's new coast guard rules officially came into effect on Saturday, granting the authorities the power to detain foreigners suspected of trespassing in the disputed South China Sea. This move by Beijing has raised concerns among neighboring countries and members of the Group of Seven (G7), who have accused China of intimidation and coercion in the region.

China has long maintained its expansive claims over nearly the entire South China Sea, dismissing competing claims from Southeast Asian nations such as the Philippines, as well as an international ruling that declared its stance as lacking legal basis. To enforce its claims, China has deployed coast guard and other vessels to patrol the waters, while also militarizing artificial islands built on several reefs.

Under the new regulations published online, China's coast guard is authorized to detain foreigners "suspected of violating management of border entry and exit." Detention can be extended up to 60 days in complex cases. The rules explicitly state that "foreign ships that have illegally entered China's territorial waters and the adjacent waters may be detained."

The actions of the Chinese coast guard have drawn strong criticism from the Philippines, with the country's President Ferdinand Marcos voicing concerns about the escalation of tensions. Manila has accused the Chinese coast guard of engaging in "barbaric and inhumane behavior," which includes using water cannons against Philippine boats and leading to multiple confrontations and collisions injuring Filipino troops.

In response, General Romeo Brawner, the Philippine military chief, announced on Friday that authorities in Manila were discussing measures to protect their fishermen, who have been instructed to continue their activities in the Exclusive Economic Zone despite the risks.

The G7, in a joint statement at the end of their summit on Friday, condemned China's "dangerous" incursions in the South China Sea and expressed opposition to China's militarization, coercion, and intimidation activities in the region. The waterway is of strategic importance, with overlapping claims from Vietnam, Malaysia, and Brunei. The recent confrontations between China and the Philippines have raised concerns of a potential escalation involving the United States and its allies.

The South China Sea is not only a vital trade route, facilitating trillions of dollars in ship-borne trade annually but is also believed to hold vast untapped oil and gas reserves and serves as a crucial fishing ground.

China has defended its new coast guard rules, stating that they are aimed at maintaining order at sea. The Chinese defense minister also gave a warning earlier this month, indicating that there are limits to China's restraint in the South China Sea. Beijing has previously expressed anger over the presence of US and Western warships in the region, seeing them as violations of its sovereignty.

Both China and the United States have experienced a series of close encounters in the South China Sea, underscoring the potential for heightened tensions and conflicts in this disputed region.