A powerful tremor has hit the Indonesian island of Sumatra - which is still reeling from a massive earthquake on Sunday.

The new quake - measuring 6.2 on the Richter scale - shook the Bengkulu region, where more than 100 people died in the original tremor.

There were no immediate reports of casualties, but residents ran screaming out of buildings.

The new quake was deeper and centred slightly south of Sunday's 7.9-magnitude tremor. It was not classified as an aftershock, Indonesia's geophysical service said.

It struck at 0645 (2345 GMT Wednesday), in the Indian Ocean about 200km (125 miles) south-east of Bengkulu. France's Strasbourg observatory measured it at 6.7.

"The quake was felt quite strongly early this morning, and everyone ran out of the buildings. Even those in tents ran out of them in panic," a photographer for AFP news agency said.

Earthquake damage is hindering the relief effort

Rescue operations in Sumatra are continuing, amid growing criticism of the slowness of Indonesia's own response.

The parliamentary speaker, Amien Rais, who has been touring the affected area, said he was ashamed that foreign governments and aid agencies had reacted much more promptly than his own government.

Soon after the latest tremor, about 100 homeless people were reported to have blocked a key road to protest at the slow government response. About 30 police struggled to defuse tensions.

Sunday's aftermath

Hospital officials and local media say around 120 people were killed and some 1,300 injured in Sunday's quake, one of the biggest to hit Indonesia in recent years.

Some 120 people died in the earthquake

Thousands of homes and other buildings were destroyed.

Foreign aid has been arriving in the region, but relief efforts have been hampered by heavy rains and flooding.

The weather and poor communications have postponed efforts to reach remote Enggano island, near the epicentre of Sunday's earthquake.

Concern had been growing for the 2,000 residents on the island, where most homes were flattened. But officials said initial reports indicated no deaths had occurred.

About 100 refugees from Enggano crossed to Bengkulu on Wednesday, saying they had lost everything and urgently needed food and shelter.

Two Dutch vessels and one Indonesian navy ship were due to deliver food and medicine by helicopter to the island on Thursday.

Seismologists said the area had been hit by nearly 400 aftershocks.