Thailand on Friday confirmed that two newborns have been diagnosed with microcephaly linked to the Zika virus for the first time in South-East Asia.
Three newborns with microcephaly, a birth defect where a baby's head is abnormally small, were under close medical supervision in a hospital that is not in Bangkok, the Health Ministry said.
"Two out of three babies with microcephaly have been confirmed to be Zika-related," Dr Vichan Pawan, spokesman for the public health ministry's department of disease control, said.
Zika is mainly spread through mosquitoes and those infected suffer flu-like symptoms. While most Zika patients recover quickly, the virus can cause brain malformations in unborn children, as well as other neurological disorders.
Vichan said there was no need to panic. "Zika is not new," he told dpa.
He also said that "microcephaly can be caused by many factors, such as infections, the baby's mother's use of alcohol and smoking," adding that "not all babies born from mothers infected with Zika will develop microcephaly."
Thailand's first Zika case was reported in 2012.
This week, the ministry announced 35 new cases of Zika throughout Thailand.
Hours earlier, US health officials advised pregnant women to delay non-essential travel to 11 South-East Asian countries because of the "uncertain risk of Zika virus infection."
The countries include Brunei, Myanmar, Cambodia, Indonesia, Laos, Malaysia, Maldives, Philippines, Thailand, East Timor and Vietnam.
The Zika virus has been present in parts of South-East Asia for several years and is endemic in some countries, the US Centers for Disease Control and Prevention (CDC) advisory noted Thursday.
Many people in the region are likely immune to it, the CDC said, adding that some people who visited the region have been infected.
Public health officials in the region downplayed the advisory.
"This is merely a general precaution," said Vichan Pawan, a spokesman in the Thai Department of Disease Control.
"Such official recommendations are nothing new," he said on Friday.
The Philippines currently has 12 cases of Zika, according to the Department of Health.
"This is for non-essential travel and therefore is not a total travel restriction," said Eric Tayag, a spokesman for the Philippines Department of Health.
"This is a travel notice so that travellers, especially pregnant mothers from the US, will be better informed on their travel and associated risks," he added.
Indonesia confirmed one case of Zika, in Jambi province on Sumatra island, in 2015. It was found during a screening programme following a dengue outbreak there in 2014. The Health Ministry said no other cases have been reported since then.