Abdul Aziz Jaafar said Malaysian and Australian aircraft were shadowing the MT Orkim Harmony, which vanished last Thursday off the southeastern Malaysian state of Johor along with its crew of 22.
"We have found the vessel and RMAF (Malaysian air force), MMEA (Malaysian coast guard) and RAAF (Australian air force) aircraft are tailing it from the air," he was quoted as saying by the state-run Bernama news agency.
The IMB said pirates were increasingly preying on slow-moving small coastal tankers and that one attack is occurring every two weeks.
Typically, armed pirates seize control of the ships and syphon off their cargoes of diesel or gas oil to other vessels before later releasing the tankers and crews.
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The MT Orkim Harmony was said to be carrying 6,000 tonnes of petrol valued at 21 million ringgit ($5.6 million).
Its crew includes 16 Malaysians, five Indonesians and one Myanmar national.
Southeast Asia saw 38 pirate attacks during January-March, or 70 percent of the global total of 54, the IMB said in an April report, calling the frequency of regional incidents "an increasing cause for concern."
Piracy in the region had been significantly reduced in the previous decade by stepped-up regional cooperation and maritime patrols, but has re-emerged.