International airlines have cancelled flights to airports near Mount Merapi, as Indonesia's most volatile volcano continues to pump out clouds of ash. Early today, boiling red lava was clearly visible in the crater of the volcano, which lies about 30 kilometres from the city of Yogyakarta. AirAsia, which is based in Malaysia, cancelled four flights from Kuala Lumpur to Yogyakarta and nearby Solo, while Silk Air cancelled two flights between Singapore and Solo. Both airlines said they were watching the situation carefully. The Jakarta Post said some domestic flights have already had to be rerouted to other airports. Transport ministry spokesman Bambang Ervan said airlines had been told to use an alternative route for safety reasons due to the volcanic ash. At least 38 people have been killed since Merapi began erupting last week. Scientists have warned that the volcano could continue rumbling for some time.