Dilawar Khan, Ziarat district chief, said: "Only one truck of tents and blankets has reached the affected areas as we were told that helicopters could not land because of aftershocks.
"It is very disappointing, we are badly in need of tents. It is extremely cold in the open."
Abdul Qadeer, his wife and their five children were forced to sleep in the open after the quake destroyed their house in Kawaz - one of about eight badly-hit villages surrounding the town of Ziarat.
He said: "It was so cold at night we thought we would freeze... we have been waiting for help but we have no tent, no food, no medicine for my children."
Fears of further tremors kept most of Ziarat's 30,000 inhabitants outdoors overnight, even if their homes had not been destroyed by the quakes.
Irshad Ahmed, a government official in Ziarat, said: "I have got my family in this open playground to sleep because you never know when the earthquake could return."
The International Committee of the Red Cross (ICRC) sent two teams to the area. Carla Haddad, a spokeswoman, said it was likely that there would be more aftershocks forcing survivors to remain outdoors in the cold.
Pakistani army helicopters resumed the search for survivors on Thursday, scouring the mountains for signs of stranded villagers.
Saleem Nawaz, commander of the paramilitary Frontier Corps in Baluchistan, said: "Along with the relief operation, we're still looking for survivors and our helicopters are still flying."
Al Jazeera's Imran Khan said that the government is not asking for international assistance.
A Pakistani military spokesman said about 250 troops and two helicopters had been sent to Ziarat from Quetta, while an aerial assessment of the damage was also under way.
|People fled their homes after the first quake hit Baluchistan province before dawn [AFP]
"The destruction is heavy, people need immediate help and we are providing assistance to the affected people," Colonel Mohammed Babar said.
Retired Lieutenant-General Faruq Ahmed, chairman of the National Disaster Management Authority, said tents, blankets and food had been sent to the area along with medical teams to treat the injured.
Maulvi Abdul Samad Akhunzada, a provincial minister, said: "Around 15,000 people have been affected, 1,500 houses have collapsed. More than 150 people have been killed and countless are injured."
"We require tents, items of food and medicines. Teams of doctors should also be dispatched immediately."
A reporter for the Associated Press news agency saw dozens of bodies and injured in a hospital in Kawaz in Ziarat district. Mohammed Irfan, a doctor, said the hospital was unable to cope with the number of injured it was receiving.
Sohail-ur-Rehman, another provincial official, said that the authorities were rushing to help about 15,000 homeless people and to bury the dead.
"Graves are being dug with excavators as we can't keep dead bodies in the open," he said.
Sanaullah, a resident, told the Associated Press news agency: "When the earthquake occurred, I was sleeping in my building with my children and suddenly I heard a noise and I recognised it was an earthquake.
"I ran to get my children. The window broke and my hand was injured and now I am waiting with my children on the roadside."
The earthquake took place at the shallow depth of 10km and hit about 70km northeast of Quetta, the US Geographical Survey said.
The Pakistani Meteorological Department said that two quakes had struck before dawn, the second of which was larger than the first.
Al Jazeera's Kamal Hyder, reporting from the Pakistani capital, Islamabad, said: "The first quake struck at 4.35am [22:35 GMT on Tuesday] forcing people out onto the streets, and then at about 5.10am the stronger second quake, measuring 6.5 on the Richter scale, is said to have hit."
Hyder said that Quetta, however, had largely escaped extensive damage.
Quetta was largely destroyed and about 30,000 people were killed in a severe earthquake in 1935.
The region's worst earthquake was in October 2005 when about 75,000 people were killed, most of them in mountainous northern Pakistan, in a 7.6 magnitude quake.