Rescue planes are struggling to reach Tonga because the airport runway is covered in volcanic ash

• New Zealand is trying to get supplies to Tonga after a volcanic eruption and tsunami.
• But ash on the runway means planes have not been able to land.

Rescue planes are struggling to reach Tonga after a tsunami because the runway of its main airport is covered in ash, reports say.

The tsunami was triggered by an underwater volcano erupting on Saturday — an explosion that also brought ash to the Polynesian island nation.

The tsunami also knocked out communications, meaning the scale of the damage, particularly on the country's most remote islands, is hard to calculate. But authorities have detailed extensive damage, and warned that people need food and clean water.

The ash from the volcano means planes have been unable to bring those supplies.

Nanaia Mahuta, New Zealand's foreign affairs minister, said on Tuesday that ash on the runway of Fua'amotu International Airport, in Nuku'alofa, had to be cleared before a jet could land.

One plane due to land on Tuesday was delayed because of the ash, New Zealand's 1 News reported.

Two hundred people were needed to sweep 100 meters (about 330 feet) of ash from the runway, the report said.

New Zealand is also sending ships with water, supplies, aid, and rescue workers, the air force said.