President Barack Obama on Monday issued an executive order imposing sanctions on four prominent figures in Burundi whom the United States says are contributing to the country's insecurity.

The freeze on assets and restrictions on visas to enter the US targets the Minister for Public Security Alain Guillaume Bunyoni, Godefroid Bizimana, the deputy director-general of the national police, Maj Gen Godefroid Niyombare, former chief of Burundi's intelligence service and Cyrille Ndayirukiye, former minister for defence.

The sanctions, aimed at two government leaders and two alleged plotters of an unsuccessful coup in May, are the latest pressures applied by Washington in an effort to halt escalating violence in Burundi.

The United States has previously suspended training for Burundi's police and military and expelled the country from the preferential trade programme known as Agoa.

"Burundi is on the precipice,” US National Security Council spokesman Ned Price declared on Monday in a statement accompanying President Obama's executive order.

"President (Pierre) Nkurunziza’s pursuit of a third term in office has precipitated a humanitarian, economic, and security crisis, forcing more than 200,000 Burundians to become refugees in neighbouring countries," Mr Price added.

"We have received multiple, credible, and ongoing reports of targeted killings, arbitrary arrests, torture, and political repression by security forces, as well as violence and abuses by youth militia affiliated with the ruling party."

At the same time, the US faulted some of Mr Nkurunziza's opponents for resorting to violence against security forces and civilians.

"The United States remains opposed to the use of violence or other unlawful means to achieve political aims or to seize power," Mr Price said.

The US also warned it may impose sanctions against more leaders in government or in the opposition.

"Now is the moment for all sides in Burundi to demonstrate the strength and leadership necessary to put aside violence and engage in an internationally mediated dialogue outside Burundi," Mr Price declared.

"We stand together with the many countries in the Great Lakes region, the African Union, European Union, United Nations, and others who have made this same appeal, and will support Burundi if it chooses this path," he added.