Indonesia had planes flying again on Tuesday after a volcanic eruption forced the country's major airports to close for days, with authorities saying that flights would resume gradually.

The disruption, caused by the eruption of Anak Krakatau, halted nearly 3,000 flights and stranded more than 340,000 passengers.

The country's main airport serving the capital Jakarta and four other airports reopened early Tuesday after authorities cleared volcanic ash from critical infrastructure.

Transport minister Dudy Purwagandhi told reporters it would take time for flight schedules to return to normal.

Dudy said there were around 178 aircraft at Soekarno-Hatta International Airport, Jakarta's main air travel hub.

"We will be operating these aircraft, but before we do so, we want to ensure their airworthiness. So, it may take a bit of extra time," he said.

"We ask for a little patience from passengers and the public, as we will be carrying out inspections to ensure that these aircraft are fit to fly," he added.

The transport minister said three flights departed shortly after the airport reopened, including two commercial flights to eastern Indonesia.

Airport operator Angkasa Pura Indonesia said in a statement that volcanic ash had been cleared from the runway and other areas to ensure the facilities were safe for flights.

Anak Krakatau, which means Child of Krakatau, sits in a strait between the islands of Java and Sumatra.

The volcano erupted at least three times on Tuesday morning alone, according to the head of the Geology Agency, Lana Saria.

It has been sporadically active since it emerged from the sea nearly a century ago in the caldera formed after the 1883 eruption of Mount Krakatau.

A 2018 tsunami triggered by a collapse of parts of Anak Krakatau killed more than 400 people and displaced thousands.