Massive evacuations have been ordered from the coast along Indonesia's Sunda Strait after warning of a possible second tsunami triggered by eruption of Anak Krakatau volcano whose alert level has been upgraded.

The Indonesian disaster agency on Friday put the total number of evacuees from danger zones at 40,386 people in the provinces of Banten and Lampung, from some 20,000 in the previous day, spokesman of the National Disaster Management Agency Sutopo Purwo Nugroho said.

A joint task force has been conducting the search and rescue for the tsunami victims trapped under the debris after the volcano-triggered tsunami on Saturday night, the spokesman said.

Meanwhile, the number of those injured in the tsunami rose sharply from over 1,400 people to a total of 7,202 people, according to the spokesman.

Indonesian volcanologist and disaster authorities have advised locals and tourists not to have activities on beaches along the strait between Java and Sumatra islands for fear of fresh tsunami.