SEOUL, South Korea — South Korea, under pressure to put on a show of force after one of its territories was shelled by North Korea last month, today went ahead with live firing exercises in disputed waters off its west coast, ignoring threats of retaliation from Pyongyang.

The drills began as reports said the North Korean regime had agreed to allow nuclear weapons inspectors back into the country, 18 months after their expulsion halted multiparty attempts to end its nuclear weapons program.

On another day of heightened tension in the region, South Korean artillery fire shook Yeonpyeong Island, the target of a Nov. 23 attack from the North in which two soldiers and two civilians were killed.

The few residents left on the island were ordered into bomb shelters during the drills, which lasted about 90 minutes. Hours after the drills ended, North Korea’s news agency quoted officials as saying that it was “not worth reacting to [South Korean] reckless provocation.”

There was never much chance of South Korea bowing to calls from Russia and China to cancel the drills. The president, Lee Myung Bak, has come under intense public pressure to take a tougher line amid anger at his lackluster response to the March sinking of the Cheonan and last month’s shelling, the first time civilians had been targeted since the 1950-53 Korean War.

Hopes for a breakthrough on North Korea’s nuclear weapons program were raised, meanwhile, with reports that the governor of New Mexico, Bill Richardson, had secured agreement for the International Atomic Energy Agency to resume inspections of its main nuclear complex at Yongbyon.

The regime had also agreed to negotiate the sale of 12,000 fuel rods, probably to South Korea, according to CNN.

Richardson reportedly proposed the launch of a military commission involving the United States, and North and South Korea, as well as a separate hotline linking the Korean militaries.

Pyongyang recently revealed that its nuclear program could be far more advanced than previously thought. It claims to have built a state-of-the-art uranium enrichment facility at Yongbyon that, theoretically, would enable it to build an arsenal of more powerful nuclear weapons.

The country is already thought to have enough fissile material to build up to a dozen plutonium-based weapons, but the proposed sale of fuel rods indicated it may be willing to scale down or end its plutonium program.

The decision to permit the first IAEA inspections since April 2009 offered a glimmer of hope at the end of a week that some had feared would put the peninsula on a war footing.

South Korea recently conducted its biggest civil defense exercise for 35 years in preparation for a possible attack centered on Seoul. As air-raid sirens sounded over the capital, traffic ground to a halt and pedestrians were ushered into buildings and subways stations. A dozen fighter jets flew across the country in a simulation of an aerial assault.

Lee, a conservative who ended the “sunshine policy” of engagement with North Korea, has faced fierce domestic criticism for his handling of the crisis as the public appetite for talks and concessions begins to falter.

He was forced to apologize for his handling of the crisis, while his defense minister promised to order air strikes should the North attack again.

“The attacks were nonsensical,” said one Seoul resident. “The North Koreans are supposed to be our fellow countrymen, so what they did, as our brothers, was morally indefensible.”

“They have showed their real face, and we can no longer trust them. They talk about the need for our countries to reconcile, but they are doing nothing of the sort. We are doing our best to promote reconciliation, but if they attack us again or continue with their provocations, then we will have no choice but to strike back.”

The United States insisted that the drills posed no threat to North Korea. In Washington, State Department spokesman Philip Crowley told reporters. “It is hard to see how a routine live-fire exercise which has been held in the past poses any kind of threat to North Korea.

“North Korea should not use any future legitimate training exercises as a justification to undertake further provocative action,” said Crowley.

A senior official in South Korea’s ruling Grand National Party described the North’s attack on Yeonpyeong as “unforgivable,” but added it was too early to abandon hope of a diplomatic on a solution.

“North Korea has made some very serious mistakes,” Kyung Kyu Sang, a senior staff director of the party’s foreign affairs, trade and unification committee, told Global Post.

“We have reached out to help in the past, but North Korea has not responded. There are those who believe the North can only be changed by force, but we have to keep talking and search for compromise. But the South Korean people don’t feel in the mood to compromise.”

Richardson, a former U.S. ambassador to the United Nations who is on a “private” visit to the North, had described the situation as a “tinderbox,” and urged Pyongyang to allow today’s drills to proceed without retaliation. “I am urging them extreme restraint,” he said in an interview with CNN. “Let’s cool things down. No response. Let the exercises take place.

“My sense from the North Koreans is that they are trying to find ways to tamp this down. Maybe that will continue today. That’s my hope. There’s enormous potential for miscalculation,” said Richardson.

North Korea’s official media, meanwhile, accused its neighbor of ratcheting up tensions by conducting the live fire drills. In typically animated language, the Rodong Sinmun, the newspaper of the ruling Workers’ Party, said: “The South Korean puppet warmongers going in league with outside forces are getting ever more frantic in their moves for a war of aggression … pushing the situation to the brink of a war.”

In New York, the U.N. Security Council failed to produce a joint statement after China refused to condemn Pyongyang for this year’s attacks.

Wang Min, China's representative at the security council, described the situation on the Korean peninsula as “perilous.”

"If a bloody clash breaks out on the Korean peninsula, that would first of all hurt the people on both sides of the peninsula and bring a national tragedy of mutual fratricide between the compatriots in the North and South," the Chinese news agency, Xinhua, quoted him as saying.

"China strongly urges both sides of the Korean peninsula to remain calm, calm and calm again, and to exercise restraint, restraint, and restraint again.”