Several international flights to and from the resort island of Bali were cancelled or diverted Thursday to avoid dangerous ash spewing from an Indonesian volcano, officials said.
Ash from rumbling Mount Bromo, a popular attraction in East Java province, had spread to the island popular with foreign tourists and surfers.
"We received information from Darwin that the ash from Bromo has reached 18,000 feet (5,500 metres) in the southeast direction and has affected some parts of Bali," transport ministry spokesman Bambang Ervan told AFP.
"As a safety precaution, we've sent out an advisory to airlines to warn them about the ash situation so air crew can avoid the affected areas," he added.
Indonesian aviation authorities were monitoring the situation but there were no plans to temporarily close the airport yet, he added.
"The airport is still open, some flights are still landing. We're checking how bad the situation is and how much worse it can get before deciding what the next step will be," Ervan said.
Australian airlines Jetstar and Virgin Blue were forced to divert Bali-bound flights from Perth, Sydney and Brisbane following the warning, Bali airport spokeswoman Sherly Yunita told AFP.
A Bali-bound Cathay Pacific flight from Hong Kong was also diverted due to the volcanic ash, she said.
Several other international flights due to leave Bali Thursday had been cancelled, she added.
Singapore Airlines cancelled two flights to and from the island and said more flights would be delayed on Thursday and Friday.
Domestic flights to and from the island were not affected, airport manager Heru Legowo said.
Mount Bromo began rumbling in November and the government had raised the eruption threat warning to the maximum red alert before lowering it last month.
Indonesia's most active volcano, Mount Merapi in central Java, has killed more than 350 people in a series of violent eruptions which started in late October.
Unlike Merapi, the countryside around Bromo is not densely populated as it lies within the Bromo-Tengger-Semeru National Park, a huge caldera containing several volcanoes.