Philippine Interior Secretary Jesse Robredo is missing after the light aircraft he was travelling in crashed into the sea, officials say.
Two other people are said to be missing after the Cessna came down in the sea off central Masbate province while trying to make an emergency landing.
An aide to Mr Robredo was rescued from the water by local fishermen.
Police said search efforts had been suspended for the evening because of darkness.
Military spokesman Col Generoso Bolina said the plane had been travelling from central Cebu city to Mr Robredo's hometown of Naga city, in Camarines Sur province.
"There was an engine problem so they sought permission to make an emergency landing at Masbate, but the plane did not make it there and crashed," Mr Bolina told reporters.
Witnesses saw the Cessna 172 crash into the sea less than a kilometre from the runway. The wreckage has not been found.
Mr Robredo's police escort managed to jump out of the aircraft and was rescued and taken to hospital with minor injuries.
Two pilots - a Filipino and a Nepali - are also missing.
Rico Puno, the under secretary in the interior ministry, said Mr Robredo had been in Cebu for a gathering of civilian volunteers assisting in police work, the Associated Press news agency reports.
Mr Robredo, 54, is a close ally of President Benigno Aquino and helped his election campaign in 2010.