North Korea says a US missile strike on Syria "proves a million times over" that it was right to strengthen its nuclear programme, state media report.

They cited an unnamed government spokesman saying Friday's strike was an "intolerable act of aggression against a sovereign state".

The strikes followed Wednesday's suspected chemical attack on a rebel-held Syrian town which killed 89.

North Korea has carried out tests to develop a nuclear missile.

The UN has banned it from missile or nuclear tests.

But it has repeatedly broken those sanctions. It has successfully tested nuclear bombs of increasing power and claims to have been able to make warheads small enough to fit on a missile, but some experts have cast doubt on those claims.

On Friday, US missiles struck a Syrian airbase, killing at least six people. It was the first US attack on a Syrian government facility, although the country had previously targeted the Islamic State group in the region.

"The US missile attack against Syria is a clear and intolerable act of aggression against a sovereign state and we strongly condemn it," a government official in North Korea said, as quoted by the KCNA news agency.

"The reality of today shows that we must stand against power with power and it proves a million times over that our decision to strengthen our nuclear deterrence has been the right choice.

"Only military power of our own will protect us from imperialistic aggression.

"We will keep bolstering our self-defensive military might in various ways in order to cope with the ever-intensifying US acts of aggression."