A strong 6.5 earthquake has rocked Indonesia's main island of Java, the US Geological Survey said, shaking buildings in the capital Jakarta.

The tremor was measured at a depth of 56 miles and struck less than a kilometre east-southeast of the coastal town of Cipatujah, USGS said.

The earthquake was felt in the capital Jakarta, about 190 miles from the epicentre, as well as several other towns on Java.

There was no immediate indication of a tsunami and authorities said there had been no casualties reported so far. There's no tsunami risk for New Zealand.

"We are still evaluating the impact of the quake and will give an update later," Nugroho said in a statement.

Jakarta resident Web Warouw was on the 18th floor of a building in the capital when the quake struck.

"Suddenly, we felt dizzy, but constantly... We then realized it was a quake and immediately ran downstairs," the 50-year-old said.

People in the coastal city of Cilacap evacuated as a precaution fearing a tsunami, although no alert had been issued for the area.

Indonesia experiences frequent seismic and volcanic activity due to its position on the Pacific "Ring of Fire", where tectonic plates collide.

An earthquake struck the country's western Aceh province in December 2016, killing more than 100 people, injuring many more and leaving tens of thousands homeless.

The quake was under the sea, off the city of Bandung where about 2 million people live.