Malaysian marine police yesterday stepped up efforts to intercept refugees from Indonesia's economic crisis amid warnings that tougher action awaits them on land. Police vessels ventured further into the Strait of Malacca, which separates Indonesia and Malaysia. Marine police commander, Senior Assistant Commissioner Abdul Malek Hamid, said the unit's craft, which had been operating off the coastline, were now patrolling international waters. Their aim is to turn back boats carrying Malaysian-bound Indonesians before they can reach shore. Police say operators of many of the boats have sophisticated navigation equipment and a knowledge of Malaysian waters, making them an elusive foe. The Deputy Home Minister, Tajol Rosli Ghazali, meanwhile said that security would be tightened at detention camps and illegal immigrants would now be treated 'like criminals'. The move followed the bloody clash between illegal immigrants resisting repatriation and police at the Semenyih camp near Kuala Lumpur on Thursday. Eight Indonesians and a member of an anti-riot unit were killed. 'We did not want to be rough with them and have them tell their friends they were badly treated,' Mr Tajol said. 'But now they leave us no choice.' He said security guards had been ordered to stop treating illegal immigrants 'softly'. Mr Tajol vowed a detailed investigation would be conducted to determine the cause of the rioting at Semenyih. 'We want to know how information on the deportation date got into the hands of immigrants, because it was supposed to be a secret,' he said. Mr Tajol added an investigation would also be held into how the foreign media obtained photographs of the rioting, when the camp was a security area. A total of 1,133 Indonesians were deported on two cargo vessels under tight security on Saturday, and another 2,000 were shipped back to Indonesia yesterday. Before that, the number in detention camps was about 9,500. The Government's aim is to clear the camps of Indonesians within a few days.