Travel bans in the Philippines, Thailand, Indonesia, Cambodia and Malaysia have been imposed to prevent travel to those countries by US citizens or permanent residents, with a focus on US nationals with valid visas.
Many travellers are concerned that they will be denied entry to the US as a result.
In Indonesia, there have been rumours of a US embassy in the country, although the US Embassy in Jakarta did not respond to questions about whether it was aware of any such reports.
While there is a travel ban in the US for Americans in the Maldives, the Maldivian authorities said on Thursday that there was no immediate threat to the country’s citizens.
Malaysia has imposed a travel restriction on US citizens and permanent residents.
“The government is taking all measures to ensure that US citizens in Malaysia can continue to travel, including checking their passports and documents,” Malaysia’s interior minister, Datuk Seri Hishammuddin Hussein, said in a statement.
There is also a ban on American business travel to Malaysia, and there is no US-based airline in the Malay Peninsula.
Bashar al-Assad, the Syrian president, is among the US officials who have been prevented from leaving the country to attend the G20 summit in Hamburg.
The ban is part of a crackdown on US-backed Syrian rebels in Syria and has led to a rise in civilian deaths.
President Donald Trump has called for an end to the travel ban, but has refused to release details of what steps he has taken to ease the restrictions.
On Thursday, Trump said the US was “keeping tabs” on travellers from the Middle East and Africa and had “not gotten the results”.
The US government did not immediately respond to a request for comment.