Darwin has been hit by a 6.4 magnitude earthquake that caused buildings across the Northern Territory capital city to shake.

Locals reported feeling tremors for about 30 seconds after 12pm on Friday, local time.

The quake originated nearly 140km away in East Timor.

The Bureau of Meteorology told concerned locals there was no tsunami threat as a result of the earthquake.

GeoScience Australia reported the quake had a depth of 28km.

There were more than 500 "felt" reports so far.

Rocked locals quickly took to social media to share their shock, after seeing buildings move and the ground shake for around half a minute.

"Wow I just felt the earth move here in Darwin! An earthquake just shook our office building here in Casuarina," one posted on Facebook.

"Just had an earthquake at Darwin. Just a little shake, nothing too serious," another said.

"The house here in Darwin was rocking! Hoping people in Timor have not experienced too much damage in that earthquake," another commented.

- by Hamish Spence, news.com.au