The warning was issued by the Meteorology, Climatology and Geophysics Agency (BMKG) Office in the Central Java town of Cilacap.
"The early warning about high waves will be valid from Tuesday 07.00 p.m. to Wednesday 07.00 p.m.," spokesman for the BMKG Office Teguh Wardoyo said here on Tuesday.

Based on satellite monitoring, 2-3 meter high waves will occur along the southern coast of Cilacap, Kebumen, Purworejo and Yogyakarta, he said.

He said 3-4 meter high waves will happen in the Indian Ocean off the southern coast of Cilacap up to Yogyakarta.

The high waves will be the result of the rising speed of winds which will blow in the easterly and southeasterly directions, he said.

"The speed of winds, which will blow over coastal areas, will reach 16 knots while over the Indian Ocean, it will reach 20 knots," he said.

He said the wind speed increase will be the impact of two storms which struck the north of the equator, around the Philippines and the Pacific Ocean.

He predicted that the impact of the two storms will gradually decline in two days' time.

With regard to the high wave early warning, he called on traditional fishermen using small boats to exercise caution and remain vigilant as 3-4 meter high waves can occur any time.

He also warned tourists against swimming along the high sea coast.

"We have communicated the early warning about high waves to all marine service users in the southern coast of Central Java and Yogyakarta," he said.

Local fisherman Misngad said the waves began to increase in height two days ago.