A magnitude 6.1 quake has struck off the coast of Papua New Guinea, but appears to have caused little damage.

The quake, centred 105km south of Kavieng at the northern tip of the island of New Ireland, struck about 9.10pm (Irish time) last night.

Port Moresby's geophysical observatory said there were no initial reports of major damage.

The quake was shallow, at a depth of only 19.5km, the US Geological Survey reported.

Magnitude 6 quakes are capable of causing severe damage, but are relatively common in Papua New Guinea, which lies on the so-called Pacific Ring of Fire, an area of intense seismic activity.

In New Zealand, authorities warned people against entering a remote southern national park while they checked for damage from the country's largest earthquake in 78 years.

Following yesterday's 7.8 magnitude quake, civil defence officials were carrying out an extensive aerial search of the South Westland region of South Island and ground parties were checking on hikers known to be in the area.

The tremor prompted a tsunami warning after it struck at 9.22pm (10.22am Irish time) yesterday, and was followed by several strong aftershocks.

However, it was centred 35km deep off the coast of the largely uninhabited South Westland region, and there were no immediate reports of serious damage.

That quake was felt as far away as Australia where a performance at Bondi Pavilion in Sydney was reported to have been cancelled and theatregoers evacuated on fears of a tsunami.

About 50 people were also evacuated from homes and resorts on Lord Howe Island, which lies between Australia and New Zealand.

However, there was only a small surge of water, about 17cm high, and the tsunami warning was cancelled after its size was confirmed when it reached the port of Bluff, near Invercargill, about an hour after the quake.