Zambia deployed the military to curb escalating political violence ahead of presidential and parliamentary elections on August 12, President Edgar Lungu said.

Two supporters of the ruling Patriotic Front party were hacked to death with machetes on Friday by attackers suspected to be members of the main opposition party, police said.

Four people were arrested in connection with the killings, police said.

In order to curb the political violence of the past two days, Lungu said he had authorised the military, including the army and air force, to help the police.

"Maintaining law and order is a daily chore of the police, but sometimes they need help from other security wings," Lungu said in a statement.

Lungu said the military would also ensure that the work of the Electoral Commission, which would conduct the polls, was not interfered with.

The main opposition grouping, the United Party for National Development, was still studying Lungu's statement, UPND presidential spokesperson Anthony Bwalya said.

Lungu is set to battle it out for a second time with businessman Hakainde Hichilema in what analysts predict will be a very tight election.