Some 20 ships loaded with illegally cut logs and sawn timber are docked outside Tanjung Balai Karimun Customs Office in Riau Islands province.

The ships were detained by the customs office while attempting to smuggle their illegal cargo into Malaysia and Singapore, the head of the office, Bambang Prasodjo, told The Jakarta Post.

Eight of the ships were detained in January, carrying over 613,000 cubic meters of illegally cut timber worth an estimated Rp 3.5 billion (US$376,344). Last year, the office detained about 30 ships.

Bambang claimed Monday there were no signs that the smuggling of illegal logs in the province's waters was slowing down.

"It is still difficult to break up the networks smuggling illegally cut logs into Singapore and Malaysia. Complicating the situation is the fact that the under the Customs Law, the smugglers are considered to be the ones carrying (the illegal goods), in this case, the captain and crew. (Arresting) the owners of the ships is outside our authority," he said.

He said smugglers carried the logs at night, even during rough weather, believing there would be fewer police patrols.

In Riau Islands, five areas are believed to be the main suppliers of illegal logs to neighboring countries. They are Tembilahan, Selat Panjang, Dumai, Tiga Island and Dabo Singkep.