Thousands of American and Filipino forces began one of their largest combat exercises in years that will include live-fire manoeuvres, aircraft assaults, urban warfare and beach landings in a showcase of US firepower in the northern Philippines near its sea border with Taiwan.

The annual exercises, called Balikatan — Tagalog for shoulder-to-shoulder — will run up to April 8 with nearly 9,000 navy, marines, air force and army troops, including 5,100 American military personnel, to strengthen the long-time treaty allies’ “capabilities and readiness for real-world challenges,” US and Philippine military officials said.

China will likely frown on the war drills given their relative proximity to Taiwan, which it claims as Chinese territory, but organisers said the exercises do not regard any particular country as a target.

“The US military and Armed Forces of the Philippines will train together to expand and advance shared tactics, techniques, and procedures that strengthen our response capabilities and readiness for real-world challenges,” said Major General Jay Bargeron, the US 3rd Marine division’s commanding general. “Our alliance remains a key source of strength and stability in the Indo-Pacific region.”

First staged in 1991, the Balikatan exercises are anchored on the 1951 Mutual Defence Treaty, which commits the United States and the Philippines to come to the aid of the other in case of an attack.

The allies aim to be strong and seamlessly braced for any security contingency as a deterrence against war. “It’s for mutual defence, never for offence,” Philippine military spokesman Colonel Ramon Zagala said.

The treaty alliance “declares formally our sense of unity and determination to mutually defend against external armed attack, so that no potential aggressor could be under the impression that either of them stands alone,” Zagala told the Associated Press.

But the governor of northern Cagayan province, where amphibious landings with limited live-fire manoeuvres were scheduled to be held in the coastal town of Claveria this week, has opposed any joint exercise utilizing gunfire, fearing it could antagonise China.

“The military consulted and asked me, but I said I cannot allow any live-fire exercise. Any exercise is OK, but live-fire,” Cagayan governor, Manuel Mamba, told the AP by telephone. “We have to engage China, but not in a war, because I know Taiwan is a powder keg.”

China, along with the US and Taiwan, have expressed interest in investing in Cagayan, which has an underdeveloped agriculture and related industries, Mamba said, adding “I’m not pro-China, I’m pro-Cagayan.”

A Philippine military official said the beach landing exercises would proceed in Claveria without any live-fire training, which will be held instead at Crow Valley, an aircraft gunnery range in Tarlac province further south of Cagayan.

The combat exercises in the northern Philippines are being held amid heightened tensions between Taiwan and China. But Zagala said most of the military manoeuvres have been planned a year ago and did not consider the recurring tensions in the Taiwan Strait.

In what it calls a warning to Taiwan independence supporters and their foreign allies, China has been staging threatening exercises and flying military planes near the island’s airspace, including on February 24, when Russia began its invasion of Ukraine.

Chinese officials led by President Xi Jinping say they are committed to using peaceful means to bring Taiwan under Beijing’s control. The US has consistently expressed its support for ensuring that Taiwan can defend itself, and Chinese military action against the island in the short- to medium-term is generally considered a remote possibility.