Seoul: In a defiant bit of timing, South Korea announced on Wednesday that key parts of a contentious US missile defence system had been installed a day after rival North Korea showed off its military power.

The South's trumpeting of progress on setting up the Terminal High-Altitude Area Defence system, or THAAD, comes as high-powered US military assets converge on the Korean Peninsula and as a combative North Korea signals possible nuclear and missile testing.

North Korea conducted live-fire artillery drills on Tuesday, the 85th anniversary of the founding of its million-person strong Korean People's Army. On the same day, a US guided-missile submarine docked in South Korea. And the USS Carl Vinson aircraft carrier is also headed toward the peninsula for a joint exercise with South Korea.

The moves to set up THAAD within this year have angered not only North Korea, but also China, the country that the Trump administration hopes to work with to rid the North of nuclear weapons. China, which has grown increasingly frustrated with its ally Pyongyang, and Russia see the system's powerful radars as a security threat.

South Korea said in a statement on Wednesday that unspecified parts of THAAD were installed. The statement said that Seoul and Washington have been pushing to get THAAD quickly working to cope with North Korea's advancing nuclear and missile threats. According to Yonhap news agency, the parts include two or three launchers, intercept missiles and a radar.

About 8,000 police officers were mobilized, and the main road leading up to the site in the country's southeast was blocked earlier Wednesday, Yonhap reported. About 200 residents and protesters rallied against THAAD in front of a local community center, some hurling plastic water bottles.

On Tuesday, North Korea conducted what it called its largest ever combined live-fire drills, near the east coast port city of Wonsan.

North Korea's official media reported Wednesday that leader Kim Jong Un personally observed the exercises, which involved the firing of more than 300 large-caliber artillery pieces and included submarine torpedo-attacks on mock enemy warships.

Along with sending US military assets to the region in a show of force, President Donald Trump is leaning on China to exert economic pressure on its wayward ally. Chinese President Xi Jinping, who spoke to Trump on Monday, is urging restraint from both Pyongyang and Washington.

In Washington, top Trump administration officials are due to brief the entire U.S. Senate on Wednesday. A rapid tempo of North Korean weapons testing in the past year has pushed Kim Jong Un's authoritarian nation closer to developing a nuclear-tipped missile that could reach the US mainland.

Republican Sen. Lindsey Graham voiced confidence that Trump won't allow North Korea to reach that point. Graham, a defence hawk who dined with Trump on Monday night, said the North should not underestimate the president's resolve.

The USS Michigan, a nuclear-powered submarine, arrived Tuesday at the South Korean port of Busan for what was described as a routine visit to rest crew and load supplies. The US 7th Fleet said two American destroyers were conducting simultaneous maritime exercises with naval ships from South Korea and Japan.

North Korea routinely accuses the United States of readying for an invasion, and threatens pre-emptive strikes to stop it. An unnamed North Korean Foreign Ministry spokesman said the US administration's policy to maximize pressure on North Korea was "little short of lighting the fuse of total war," the state news agency reported Tuesday.

The streets of Pyongyang, however, were quiet for Tuesday's anniversary, which was overshadowed by April 15 celebrations for the birthday of the nation's late founder Kim Il Sung, and were marked by a missile test the following day.

The Trump administration is also upping the ante diplomatically. On Friday, Secretary of State Rex Tillerson will chair a special meeting of the UN Security Council.

Tillerson will be "very vocal" about nations enforcing sanctions on North Korea, State Department spokesman Mark Toner said. Trump said Monday the council must be prepared to impose stronger sanctions.