Flights into and out of Japanese airport cancelled after US-made bomb discovered during construction

An airport in northern Japan was closed on Tuesday after construction workers found an unexploded bomb believed to be from the second world war.

All 92 flights into and out of Sendai airport were cancelled after the 250kg (550lb) bomb was uncovered during construction near a runway.

The American-made device appeared to have a working detonator, and a military bomb squad was considering whether to move it or explode it on the spot.

Sandbags were piled up around the bomb, and officials said evacuations of nearby homes were being considered. They said the area had been sealed off and there was no immediate concern that the bomb would explode.

Sendai airport, a regional hub for travel into northern Japan, was closed for months due to severe damage from last year's tsunami. It is still undergoing reconstruction.

Officials said the airport would reopen as soon as the bomb was considered secure, possibly by Wednesday morning. But they said it could take a week to dispose of it or erect barriers to prepare the site for a controlled detonation.

The US heavily bombed Japanese cities during the second world war, and finding unexploded bombs is not unusual, even 67 years after Japan's surrender. Dozens of duds are uncovered in Tokyo each year, and even more are found on the southern island of Okinawa, the scene of some of the most intense fighting during the war.

Many of them are found at construction sites. The rusty condition of the bombs can make them prone to detonate when moved, but injuries are rare. Experts say it could take several decades to remove all of the unexploded ordnance.

Last week hundreds of residents in central Tokyo were evacuated so that bomb squads could remove a 220kg dud buried there.