A strong 7.0-magnitude earthquake was recorded in the sea north of the main Indonesian island of Java, the US Geological Survey (USGS) said on Friday, with no immediate reports of damage or casualties.
The quake struck at 4:55 pm local time (0955 GMT), the USGS said, with Indonesia's geological agency ruling out a tsunami after the epicentre was detected at a depth of 594 kilometres (370 miles).
Indonesia experiences frequent quakes due to its position on the Pacific "Ring of Fire", an arc of intense seismic activity that stretches from Japan through Southeast Asia and across the Pacific basin.
Friday's quake hit roughly 160 kilometres northwest of Surabaya, Indonesia's second-most populous city that is home to more than two million people.
The tremor was felt over a large part of Java and as far away as the islands of Bali and Lombok.
"In Surabaya, it was barely felt, but some lamps were swaying," said an AFP reporter who felt the tremor "for a while".
Klistjart Tarissa, 25, a resident of Bandung in West Java, told AFP she "was a bit panicked because I was (on the) second floor and I didn't know whether the quake's intensity was getting bigger or smaller".
In Yogyakarta, a teacher who had been hosting an online lecture said the quake interrupted his class.
"I thought the wind was blowing, causing my keys to rattle, but it lasted for a while," said 33-year-old Simon Arsa Manggala.
"After that, I felt a tremor which was quite strong and long."
A 5.5-magnitude aftershock was recorded by Indonesia's geological agency in the same area about an hour after the main tremor.
Abdul Muhari, spokesman for the national disaster mitigation agency, said the earthquake was not expected to cause much damage because of its great depth.
A 5.6-magnitude quake hit West Java province, on the same island, in November, killing 602 people.
Most of the victims of that earthquake were killed when buildings collapsed or in landslides triggered by the tremor.
A 6.1-magnitude earthquake struck off Sumatra island in Indonesia on April 3, shaking homes but causing no casualties or damage.