Hundreds of tourists have fled a volcanic eruption at a popular Indonesian hiking destination, an official said Wednesday, expressing fears some may have stayed behind to document the natural wonder.

Around 1,000 tourists, including about 600 foreigners, were believed to be in the area when Mount Barujari sent columns of ash and smoke shooting high into the sky over holiday island Lombok Tuesday, according to the official disaster agency.

Barujari is a small cone within the crater of Mount Rinjani, Indonesia's second-highest volcano and a major attraction for foreign tourists visiting the archipelago.

Most visitors were believed to have safely fled the area once authorities alerted them after Barujari sent a two-kilometre (1.2-mile) cloud of hot gas into the air, disaster agency spokesman Sutopo Purwo Nugroho said.

Officials were dispatched to the national park surrounding Rinjani to ask people to leave and help evacuate them if necessary.

Nugroho said officials had so far confirmed about 260 tourists had left the national park.

But the majority of others were also believed to have left the area, although authorities were having difficulty counting them as they had flooded out through unofficial exits, he said.

Officials however had difficulty persuading some tourists to leave a three-kilometre safety zone established around the volcano as they wanted to get pictures of the eruption.

"The local disaster agency said that some tourists did not want to leave," Nugroho said.

"They wanted to record the eruption of Barujari and in some cases hid from officials. They knew it was dangerous but they still wanted to document the eruption."

Muhammad Rum, a local spokesman for the disaster agency, added the eruption was not major and he believed all the hikers had now left the area.

All those who had descended were "in good condition and healthy", he added.

"Many of them even videotaped the eruption while enjoying the beauty of the mountain," he added.

The threat level of the volcano was raised Tuesday as Barujari erupted, but remains two steps below the highest level on a four-point scale.

Some flights to and from the nearby resort island of Bali were cancelled overnight Tuesday to Wednesday, but Lombok's international airport remains unaffected.

Flight disruptions due to drifting ash clouds are not uncommon in Indonesia, which sits on a belt of seismic activity known as the "Ring of Fire" and is home to around 130 active volcanoes.

An eruption at Rinjani last month forced the closure of Lombok airport and disrupted some flights to neighbouring Bali.