Tensions are rising across Japan before the scheduled docking of a controversial North Korean ferry Monday at the northern Japanese coastal city of Niigata. Japanese police have defused two bombs planted by suspected rightists near a North Korean-linked bank and a building of a pro-Pyongyang residents' group in the western Japanese city of Fukuoka.

The Japanese police and coast guard are on heightened alert in anticipation of the Mangyongbong 92's expected arrival Monday for a two-day port call in the northern city of Niigata. The ship last docked there in January, but subsequent trips were canceled after Japanese police vowed to search it thoroughly and after angry protesters mobbed the pier.

Tokyo accuses the vessel of being a conduit for drug smuggling, illegal cash transfers, and spying activities. It is one of the only semi-regular means of conveyance between isolated North Korea and ethnic pro-Pyongyang Koreans living in Japan.

Ethnic Koreans, many descendants of those forcibly taken to Japan during its 1910-1945 colonial rule of Korea, are not usually granted Japanese citizenship and often reflect the divided loyalties of communist North Korea and capitalist South Korea.

Police were patrolling areas of the western cities of Fukuoka and Okayama after several Japanese news organizations received threatening phone calls from a suspected right-wing activist protesting the Mangyongbong's port call in Niigata. Before the calls, police in Fukuoka found apparent explosive devices near the North Korea-linked Chogin-nishi Shinkumi Bank, and a building of the pro-Pyongyang General Association of Korean Residents in Japan, called Chongryun.

Before a police bomb squad removed the objects, 120 local residents were evacuated. Meanwhile, police said a bullet had been fired at the bank's headquarters in the city of Okayama. No injuries were reported.

Police are investigating whether these incidents are linked to an unexploded bomb and firing of a bullet last month in Niigata, near where the ferry is to dock.

The Mangyongbong's contentious port call is emblematic of the tensions surrounding inter-Korean relations. Sunday, in Taegu, South Korea, a North Korean journalists' delegation scuffled with anti-Pyongyang protesters at the World University Games.

It also comes a few days before planned six-way talks in Beijing to attempt to resolve the 10 month crisis surrounding Pyongyang's nuclear programs. Those talks will involve the two Koreas, the United States, China, Japan and Russia.