The US State Department has warned of possible terrorist attacks in a revised travel advisory for Sri Lanka, after a series of deadly blasts killed nearly 300 people -- including Americans -- in the island nation on Easter Sunday.
Sunday's attacks saw suicide bombers target churches during Easter services and high-end hotels in the capital Colombo.
Secretary of State Mike Pompeo said "several" Americans were killed -- the worst violence to hit Sri Lanka since a long and bloody civil war ended a decade ago.
The latest US travel advisory urged "increased caution."
"Terrorist groups continue plotting possible attacks in Sri Lanka," it said.
"Terrorists may attack with little or no warning, targeting tourist locations, transportation hubs, markets/shopping malls" and other public locations like hotels, clubs, restaurants, and places of worship.
Travel advisories from other nations like Australia and Ireland also suggest citizens exercise caution while in Sri Lanka.
Authorities have said citizens of India, China, Denmark, the Netherlands, Japan, Portugal, Britain, and Turkey died in the attacks.
The US embassy in Colombo said it would remain closed to the public on Monday and Tuesday, but will continue to provide citizen services.
There has been no claim of responsibility yet for the attacks, which the White House described as "despicable and senseless."
Security has been ramped up across Sri Lanka as security forces hunt for suspects, with 24 people arrested so far. Wary of sparking ethnic and religious tensions, the government has given few details about those detained.
Authorities have said, however, that they are looking into whether the attackers had any "overseas" links.
Travel guide book publisher Lonely Planet in October named Sri Lanka as its top destination for 2019, describing it as "the island opening up to new travellers like never before".