North Korea has fired an unidentified type of ballistic missile, South Korea's Yonhap news agency reports.

Pyongyang has conducted a number of nuclear tests in the past year.

North Korean leader Kim Jong-un said in January that the country was close to testing long-range missiles capable of carrying nuclear warheads.

North Korea's repeated missile and nuclear tests and aggressive statements continue to alarm and anger the region.

On a visit to South Korea last week, US Defence Secretary James Mattis said that any use of nuclear weapons by North Korea would be met with an "effective and overwhelming" response.

He also reconfirmed plans to deploy a US missile defence system in South Korea later this year.

How advanced is North Korea's nuclear programme?

North Korea's missile programme

North Korea conducted its fifth test of a nuclear device last year, and claims it is capable of carrying out a nuclear attack on the US, though experts are still unconvinced that its technology has progressed that far.

It has also said in recent weeks that it has a new intercontinental ballistic missile, capable of reaching the US mainland, which it is prepared to test launch at any time.