In his first televised speech since last week's power grab, General Min Aung Hlaing said the country's election commission and civilian leaders had failed to properly investigate allegations of rigging in November's election.

"In order to maintain and protect the democratic system, Tatmataw (the armed forces) in line with the 2008 constitution, declared a state of emergency," he said.

The army has announced a one-year state of emergency and on Monday imposed martial law in parts of Mandalay, sections of Yangon and other townships following nationwide demonstrations against the coup.

But Min Aung Hlaing, handed sweeping powers following the coup, insisted that the new military junta would be "different" from the army's previous 49-year reign, which ended in 2011.

"After the tasks of the emergency period are completed, free and fair multi-party general elections will be held according to the constitution," he said.

"The winning party will be transferred state duty according to democratic standards."

The general said that foreign, economic and administrative policy would not change under military rule.

The coup, in which civilian leader Aung San Suu Kyi and dozens of other members of her National League for Democracy party were detained, ended a decade of partial civilian rule in Myanmar and triggered international condemnation.