(Adds NZ foreign ministry, Red Cross comments)
WELLINGTON, Jan 16 (Reuters) - Pacific nations and humanitarian groups struggled to establish communications with Tonga on Sunday after a tsunami triggered by a massive volcanic eruption cut telephone and internet connections, raising concerns for the tiny island nation.
An underwater volcano off Tonga erupted on Saturday, triggering tsunami warnings and evacuation orders on the shores of Tonga as well as several South Pacific islands, where footage on social media showed waves crashing into coastal homes.
Internet and phone lines went down at about 6.40 p.m. local time on Saturday, leaving the 105,000 residents on the islands virtually uncontactable.
"The images of the volcanic eruption in close proximity to Tonga are hugely concerning," Jacinda Ardern, the Prime Minister of New Zealand, located about 1,481 miles from Tonga, said in a statement on Instagram.
"Communication as a result of the eruption has been difficult, but our defence force team and Ministry of Foreign Affairs are working as we speak to establish what's needed and how we can help," she said.
The New Zealand foreign ministry said there were no reports of injuries or deaths as yet but communications were limited.
Ardern will address the media at 3 p.m New Zealand time (0200 GMT) to give an update on the situation.
The International Federation of Red Cross and Red Crescent Societies (IFRC) Pacific Office in Suva, Fiji said it was monitoring the situation and had no updates on damages or casualties.
Tongan churches in New Zealand organised prayers for their families back home.
"We pray God will help our country at this sad moment. We hope everybody is safe...," Maikeli Atiola, the Secretary of the Wesleyan Church of Tonga in Auckland said, Radio New Zealand reported.
The Hunga-Tonga-Hunga-Ha'apai volcano has erupted regularly over the past few decades but Saturday's eruption was so loud that residents parts of faraway Fiji and New Zealand said they heard it.
Satellite images captured the volcanic eruption on Saturday as the explosion sent plumes of smoke into the air and about 12 miles above the sea level.
The sky over Tonga was darkened by the ash.
The eruptions triggered tsunami warnings across the Pacific, with the United States and Japan urging people on their Pacific coastlines to stay away from the shores.
Australia issued a marine tsunami warning for the New South Wales coastlines, Lord Howe Island and Norfolk Island, and said local beaches along the state's coast have been closed. A tsunami advisory was also issued in New Zealand. (Reporting by Praveen Menon; Editing by Leslie Adler & Simon Cameron-Moore)
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