Mohammad Yasin, 27, who worked as a volunteer in the immediate aftermath of the October 2005 earthquake in northern Pakistan, was in his home in Ziarat, Balochistan Province, and witnessed this morning's quake:
"Just after 4am Wednesday morning, I felt tremors that woke me up. Soon after I went back to bed, I heard crashing sounds and the earth shook violently. The building opposite to where I live was shaking and some rubble fell from it as I watched. It was terrifying."
According to the US geological survey, the earthquake measured 6.4 on the Richter scale, with its epicentre in the Chiltan mountain range about 70km northeast of Balochistan's provincial capital, Quetta.
It struck at 5.10am, as most people slept. The scenic resort town of Ziarat, some 120km northeast of Quetta, has been the worst hit.
Local media were reporting that 150 had died in Ziarat alone. Scores of others are feared dead or injured across the region, with the towns of Pishin, Qila Abdullah, Chaman, Loralai, Sibbi and Mastung all badly affected.
"Reports of casualties are coming in, but we have no definite figure or data yet," the military spokesman in Quetta, Maj Shahbahat Hussain, said.
The Balochistan minister for revenue, Zamrak Khan, put the death toll at 100 but told IRIN it "could rise".
An emergency was declared at hospitals across the affected area and all staff ordered to report immediately for duty.
Eyewitnesses report seeing massive landslides on the hills that stand by the road leading from Ziarat to Quetta.
"I set off on the three-hour drive to Quetta with a neighbour whose 10-year-old daughter had broken an arm when a falling beam hit her as she slept. The hillsides are destroyed in many places. Huge boulders have slipped down and hundreds of houses have been damaged," Ayaz Khan, a bus driver, told IRIN.
In Quetta, people spoke of panic as tremors were felt and people raced out of their homes. However, some residents say the damage in the city itself has been limited.
Deputy director of the geological survey of Pakistan, Asif Rana, told IRIN that "aftershocks are continuing" and more are expected over the next 48 hours.
"These additional tremors are adding to the fear. We heard screams immediately after the quake and people are still buried under rubble," Muhammad Yasin told IRIN. Around 500 houses are reported to have collapsed in and around Ziarat, according to local officials.
Qamar-uz-Zaman, director of the General Meteorological Department, said seven aftershocks had been felt and more were likely in the area.
Relief work kicks off
There have been some reports that relief efforts have kicked off. The Inter Services Public Relations (ISPR) for the Pakistan military said Frontier Corps troops had been dispatched to help with relief work.
The chairman of the National Disaster Management Authority (NDMA), Farooq Ahmed Khan, said 1,000 tents and 1,500 blankets, as well as other relief supplies had already been dispatched to affected areas.
The NDMA was set up in the aftermath of the October 2005 quake, which killed 74,000 people, in a bid to more effectively coordinate rescue and relief efforts after natural disasters. It is hoped the lessons learnt from that disaster will help Pakistan tackle the latest quake.
International relief organisations were reportedly in Islamabad "standing by" but had not been called on to assist. The Inspector-General Frontier Corps, Balochistan, Maj-Gen Saleem Nawaz, asked the media to "help inform people about expected aftershocks and ongoing rescue efforts".
Quetta and its environs are in an active seismic zone. In 1935 an earthquake killed 30,000- 50,000 people in the city.
"We are just thankful this time around Allah (God) seems to have been kinder," said Zahida Bibi, 65, who can recall hearing about that disaster from her parents who lived through it and narrowly survived.