Malaysian Prime Minister Najib Razak's chief of staff and a former ambassador to the United States, who was also a senior member of Najib's party, were among six people killed in a helicopter crash near the capital, officials said on Sunday.

Witnesses told state news agency Bernama they saw the helicopter explode in midair before it crashed into the ground in the town of Semenyih outside Kuala Lumpur late on Saturday.

The Prime Minister's Office said the helicopter was carrying guests back from a wedding reception for Najib's daughter.