The largest quake, which measured 7.6 magnitude, impacted on a wide area along the northern coast and through the Highlands provinces.
Twelve deaths have been confirmed along with hundreds of injuries, Radio New Zealand Pacific reported.
PNG Red Cross secretary general Valachi Quagliata said the Red Cross knew that between five and ten thousand people lost their homes to landslides and other factors.
Many areas affected had not been reached. "We haven't actually reached them all because our volunteers are trying to attend to the cases which they have found out about. But in the remote places, we haven't attended to them as yet."
He said many of the houses wrecked were of modern construction.
Quagliata said one of the main holdups for his volunteers is having material such as tents, tarpaulins and mosquito nets available.
He said the Red Cross may soon begin seeking assistance from overseas.