The epicentre was 377km from American Samoa capital Pago Pago, which was hard-hit by a magnitude 8 earthquake and tsunamis on Tuesday.
Tonga is west of the international dateline and a day ahead of the Samoan islands.
The confirmed death toll from Tuesday's tsunamis stood at 149 in Samoa, 31 on American Samoa and nine in neighbouring Tonga.
|Officials in Samoa fear the tsunamis destroyed whole towns on outlying islands [Reuters]
Dozens of aftershocks have rocked the region since Tuesday, keeping residents on edge as they try to pick up the pieces in the wake of the tsunami.
Many of the dead have been buried in unmarked beachside graves as the gruesome task of recovering bodies from destroyed villages continues.
On Samoa, survivors have been clearing debris and beginning to rebuild their shattered homes, but others remained in nearby mountains afraid to return to the coast.
Officials fear whole towns have been destroyed on outlying islands and hundreds of people remain missing. Thousands of others have been made homeless and hundreds injured.
Tuilaepa Lupesoliai Sailele Malielegaoi, the Samoan prime minister, was near tears on Wednesday night as he urged the tiny South Pacific island nation to rebuild, calling on church leaders to pray as Samoans grieved.
Recovery workers have been frantically trying to recover bodies decomposing in the South Pacific heat.
"The bodies we recovered today were not a pretty sight and that is why we're trying to work hard and fast as we can," said Seve Tony Hill, Samoa's fire chief.
"Most of the bodies we've come across are young kids and babies, who were already in a bad state of decomposition, it just makes you want to cry," Hill told local media.
Aid officials have warned of disease outbreaks with more than a thousand people crowded into makeshift camps around Apia and a lack of fresh water.