An Air Self-Defense Force F-4 fighter jet caught fire Wednesday shortly before it was to depart for a training flight from a base in Ibaraki Prefecture, the ASDF said.

No one was hurt in the incident as the two pilots escaped safely, according to the ASDF.

The plane's landing gear malfunctioned for unknown reasons, which was followed by a fire breaking out from an apparent leak in a fuel tank.

The plane was heading for a runway at Hyakuri Air Base, at around 11:45 a.m. when the incident occurred.

Black smoke was seen billowing from the aircraft at one point. The fire was put out about 20 minutes later, the Air Self-Defense Force said.

"It is a serious problem regarding flight safety," Defense Minister Itsunori Onodera told reporters. He said he had not heard about any similar trouble in the past but that the ASDF will confirm the safety of each of the F-4s before they fly again.

The base shares the airfield with Ibaraki Airport. The incident did not interrupt operations at the airport, according to the prefecture.

The F-4 fighter jets are aging and the Defense Ministry plans to replace them with F-35 stealth fighter jets, which will be deployed from the end of fiscal 2017.