The white-hulled Mangyongbong-92, with North Korea's red star emblazoned on its funnel, has long been a focus of suspicion during its regular visits to the northern Japanese port of Niigata. But tensions have peaked amid new allegations the boat is a conduit for communist espionage.
The visit, the first in seven months, tested already icy relations between Japan and North Korea just days before top diplomats from the neighboring nations meet at six-nation talks in Beijing on Pyongyang's suspected nuclear weapons programs.
After combing the ship for safety and customs inspections, Japanese authorities said there was a problem with five points, and that the ship couldn't leave for its homeport of Wonsan, North Korea, until they were fixed. The ship had been scheduled to leave Tuesday morning.
About 1,500 police, some brandishing riot shields, helmets and batons, greeted the ship when it pulled into harbor Monday morning.
They stood guard as right-wing extremists blasted the incoming ship with chants of "Go Home!" Supporters of a group of Japanese kidnapped by North Korea decades ago to train communist spies chimed in, demanding the return of loved ones.
At the ferry terminal, pro-Pyongyang Japanese residents waved North Korean flags under a banner reading: "Long live the glorious fatherland, the Democratic People's Republic of Korea."
Japanese officials, from the transportation, health and justice ministries, had promised to search every inch of the ship for everything from illicit drugs to illegal immigrants while also checking for routine safety inspections and even rodent infestations.
If violations were found, Japan warned that the ship could be detained or sent home without picking up its North Korea-bound passengers and cargo.
The Mangyongbong came under suspicion earlier this year, when two alleged North Korean defectors testified before the U.S. Congress it had ferried from Japan up to 80 percent of the parts used in Pyongyang's missile program. Tokyo says the boat traditionally ships back the majority of millions of dollars in cash sent home every year from North Koreans living in Japan.
The ship has not made its regular trip to Niigata since January, and two port calls in June were scrapped amid plans for equally intrusive inspections and angry pier-side protests ahead of its arrival.
The Mangyongbong had passed most of the early inspections.
No immigration violations were found among the 34 disembarking passengers and the boat was equipped with a special automatic identification beacon previously thought by Japanese officials to be missing and posing a safety violation. In addition, no irregularities were found in either the incoming cargo or personal luggage, Coast Guard spokesman Yoshiaki Shibuya said.
But Transportation Ministry officials in charge of conducting Port State Control safety inspections later said there were five safety hazards: No fire damper in a kitchen exhaust duct, a lack of emergency exits signs meeting height and lighting specifics, lack of a wireless phone for communicating with airplanes in emergencies, a faulty divider for oil and bilge water and the lack of a fire extinguisher that uses sea water.
The boat could not set voyage until the problems were fixed, the ministry said in a statement.
Japanese customs officials had cleared most of the 60 tons of cargo bound for North Korea, the bulk of which was clothes, food, refrigerators and used automobiles.
The General Association for Korean Residents in Japan, a pro-Pyongyang group, was not immediately available for comment on the failed inspections. But earlier, its spokesman So Chung-On had criticized Japan's extensive inspections as an "overreaction."
Disembarking passengers called the ship a lifeline of humanitarian contact between North Koreans in Japan and in their homeland, not a smuggling boat.
But Japanese activists pushing for Tokyo to adopt a hardline stance toward North Korea demanded the government stay firm.
"We want the government to thoroughly inspect the Mangyongbong and keep pressure on North Korea," said Toru Hasuike, whose brother is one of five Japanese who was kidnapped by North Korean spies in the 1970s and released last October.
Japan, the United States and South Korea have discussed cracking down on North Korean shipping as a way of pressuring the North to abandon its nuclear weapons program.
The North is suspected of shipping in missile parts and shipping out weapons to other countries; last fall, a North Korean vessel en route to Yemen carrying SCUD missiles was briefly detained.
The nuclear standoff began in October when North Korea told a U.S. envoy that it had launched a program to turn uranium into nuclear fuel. That led the U.S. to halt fuel shipments that took place under a 1994 deal in which North Korea vowed to end nuclear development.
When the fuel shipments stopped, North Korea kicked out nuclear inspectors and vowed to begin reprocessing fuel rods into plutonium for nuclear weapons. The CIA already believed the North has one or two nuclear devices.