North Korea's latest test of its Musudan mid-range missile indicates that the country is capable of firing a missile with a range of 3,500 kilometers, South Korea's military officials said Friday.

In the latest test fire of the intermediate-range ballistic missile (IRBM) which the North calls the Hwasong-10, one of the two that were launched soared to an altitude exceeding 1,000 km and flew some 400 km before hitting the East Sea.

The North launched the missiles on Wednesday near Wonsan on their east coast, but the first crashed without flying very far. It was the first time a North Korean IRBM has flown that far. All previous launch attempts ended in failure, having either exploded or crashed.

The military officials said the Wednesday launch was likely to be aimed at testing the IRBM's engine performance or its maximum flight range. It said the latest test showed tangible gains vis-a-vis the past.

"In terms of engine performance, the country seems to have verified (engine) credibility to some extent," an official said, asking not to be named because of the sensitivity of the issue.

The test has also shown that the missile could have a maximum flight range of 3,000 to 3,500 km, the official said, citing the military's calculation results based on the recent flight performance.

South Korea's military has said North Korea fired the sixth Musudan at a deliberately high angle so it would achieve its maximum altitude rather than flying far, which experts attribute to North Korea's hesitation to inflame its neighbors. It said the move can help the North see if the missile can reach a high altitude without any problems.

Reaching a very high altitude can allow Pyongyang to test its warhead re-entry technology, a crucial part of any long-range nuclear-tipped missile that flies though space before re-entering the earth's atmosphere to hit its target. During re-entry the warhead must be able to withstand considerable heat and pressure. The military needs more time to confirm whether the latest test provided meaningful results in terms of re-entry technology.

North Korea had five back-to-back launch failures with Musudan before finding success on the sixth launch, "Seeing from our standard, (Musudan) lacks credibility as a weapon," the official said. "It seems like (North Korea) may need additional test launches down the road."  Other officials, on the other hand, said the latest North Korean launch result showed Musudan is beyond South Korea's current missile interception capability.

The sixth Musudan missile is presumed to have flown at a speed and altitude that clearly surpasses the capacity of South Korea's Patriot missile interception system, the officials said. He said that it is because of such threats that South Korea and the United States began negotiations on deploying the advanced Terminal High Altitude Area Defense on South Korean soil. The North's IRBM is about 12 meters long, weighs between 18 and 20 tons and can reach speeds of up to Mach 16.

North Korea deployed Musudans with its forces in 2007, but the IRBM had never been tested before the North conducted its first trial launch on April 15, the birthday of North Korea's founding father Kim Il-sung. (Yonhap)