Aid agencies in the Solomon Islands are starting to see outbreaks of disease in evacuation centres where people have gathered after devastating flooding and strong earthquakes.
The Pacific nation continues to be rattled by strong earthquakes, the latest magnitude 6.1 on Monday. The quake was about 90km south of the city of KiraKira on San Cristobel, the United States Geological Survey says. There were no immediate reports of casualties or damage.
On Sunday, a 7.4-magnitude earthquake struck at 11.36pm (local time) at a depth of 35km and was centred 111km south of Kirakira and 321km south-east of the capital Honiara.
A 7.6 tremor had woken residents of Honiara early on Sunday. It struck about 300km from the capital and was followed 10 minutes later by a 5.9-magnitude aftershock.
The quakes come as thousands of Solomon Islanders remain in evacuation centres following devastating flash floods on 3 April which left more than 20 dead. Several more are still missing in Honiara after the city's main river burst its banks following days of heavy rain.
Oxfam deputy country director Belinda Barnard said centres set up for people fleeing the floods had struggled to cope from the start and a lack of sanitation is beginning to cause problems.
"Particularly in children, there are some signs of outbreaks starting to show. Specifically the kinds of things that are being identified are the ones you would expect - diarrhoea, malaria, dengue - but also some concerns about diseases that are spread through an influx in the population of rats."
Aid agencies and the government were trying to find longer-term accommodation for the 10,000 people still living in evacuation centres, Ms Barnard said.
World Vision's Dwain Hindriksen, who is based in rural Guadalcanal, said there were no reports of significant earthquake damage, which was a relief given the aftermath of the flooding remained challenging.
"We're still working round the clock to reach affected communities and distribute relief items."
Oxfam Solomon Islands director Katie Greenwood said there were reports after the first earthquake that one person had died as they were trying to go to higher ground.
Ms Greenwood told Radio New Zealand's Morning Report programme on Monday that Solomon Islanders were resilient but the natural disasters had taken a toll.
"There have been, in fact, 36 earthquakes and tremors and aftershocks ... over that last 24-hour period and with what has already happened it does certainly take its psychological toll."
A tsunami warning was issued for the Solomon Islands, Vanuatu and Papua New Guinea by the Pacific Tsunami Warning Center following the second quake but later lifted.
A potential tsunami advisory threat issued for New Zealand was also cancelled soon after. However the Ministry of Civil Defence said north-western parts of the North Island and the west coast of the South Island may experience strong currents over the next 24 hours, and it is strongly advising caution
NZ to send more help
A 10-person medical team will leave New Zealand for the Solomon Islands on Tuesday as the islands deals with the aftermath of natural disasters.
Foreign Affairs Minister Murray McCully said New Zealand had already contributed aid and more help was being arranged.
The medical team will be based at the National Referral Hospital in Honiara, and 10 more staff are on stand-by to relieve the first team when needed.
Mr McCully told Morning Report New Zealand had also been asked for help with repairing bridges and was looking at what it can do.
GNS seismologist John Ristau told the programme further earthquakes in the next few days are unlikely, but possible. He said quake on Sunday night was probably triggered by the earlier 7.6 tremor in the extremely active seismic area.
The Solomons are part of the "Ring of Fire", a zone of tectonic activity around the Pacific that is subject to frequent earthquakes and volcanic eruptions.
A 6.1-magnitude tremor hit the Solomons on Saturday and a powerful 7.1-magnitude earthquake and 6.7 aftershock struck off Papua New Guinea's Bougainville island on Friday, to the west of the Solomons, AFP reports.
In February last year, the Solomon Islands was hit by a major 8.0 magnitude quake that generated small but deadly tsunami waves which washed away houses and reached as far away as Japan. In 2007, a tsunami following an 8.0-magnitude earthquake killed at least 52 people in the Solomons and left thousands homeless.