Updated

A barrage of ballistic missiles that North Korea test-fired over the weekend may have included a new type of a Scud with an extended range and improved accuracy that poses a threat to Japan, a South Korean newspaper reported Monday.

Pyongyang launched seven missiles into waters off its east coast Saturday in a show of force that defied U.N. resolutions and drew international condemnation.

On Monday, South Korea's mass-circulation Chosun Ilbo newspaper reported the launches were believed to have included three Scud-ER missiles with a range of up to 620 miles.

The paper said the Scud-ER has a longer range and better accuracy compared with previous Scud series so is "particularly a threat to Japan."

The Chosun Ilbo, citing a government source it did not name, said the other four missiles were two Scud-C missiles with a range of 310 miles and two medium-range Rodong missiles that can travel up to 810 miles.

Five of the seven missiles flew about 260 miles from an eastern coastal launch site and landed in one area, meaning their accuracy has improved, the paper said.

South Korea's Defense Ministry said it could not confirm the report, saying details of the launches were still under investigation.

One Defense Ministry official told The Associated Press on Sunday that the missiles were likely capable of striking key government and military facilities in South Korea, and that they appeared to have traveled about 250 miles. The official spoke on condition of anonymity citing department policy.

The launches on July 4 — the U.S. Independence Day holiday — also appeared to be a poke at Washington as it moves to enforce U.N. as well as its own sanctions against the isolated regime for its May 25 nuclear test.

Adm. Mike Mullen, chairman of the U.S. Joint Chiefs of Staff, warned they were "very destabilizing, potentially."

But Vice President Joe Biden indicated the U.S. would not be baited by attacks on the day Americans celebrated their independence. On ABC, he described the flurry of rockets as "attention-seeking behavior."

He added: "I don't want to give the attention."

U.N. Secretary-General Ban Ki-moon said he is concerned about the missile tests, which defied Security Council resolutions. He told reporters Sunday that North Korea's communist regime has closed all doors to communication and dialogue.

Officials at South Korea's unification and defense ministries said Monday that Ban appeared to be emphasizing the launches would further deepen the North's isolation. Nevertheless, the two Koreas have not severed all contact despite increasingly strained ties. They have held several rounds of talks on their joint factory park, the latest last week, and are still connected by several hot lines.

North Korean state media have not specifically mentioned the launches but boasted Sunday that the country's military could impose "merciless punishment" on those who provoke it.

"Our revolutionary forces have grown up today as the strong army that can impose merciless punishment against those who offend us," the North's main Rodong Sinmun newspaper said in a commentary, carried by the official Korean Central News Agency.

The North has engaged in a series of acts this year widely seen as provocative. It fired a long-range rocket it said was a satellite in early April, and in late May it carried out its second underground nuclear test following the first in late 2006.

Another defense official said Monday that no signs of additional North Korean launches have been detected but that the South Korean military was closely monitoring the North's military. He also spoke on condition of anonymity citing department policy.

The North has warned ships to stay away from a large area off the east coast until July 10, leading to concerns more missiles could be fired.