Three Afghans including a police officer were killed in a suicide attack in the southern Afghan city of Kandahar early on Monday, the interior ministry said, two days after a deadly bombing in the capital.

Two others, among them another police officer, were wounded in the car bombing on Monday, near a building used by the Office of the United Nations High Commissioner for Refugees (UNHCR).

We are aware of an explosion which took place earlier this morning in the vicinity of the UNHCR guest house, United Nations spokesman Dan McNorton said.

All our international staff are accounted for ... the incident is still ongoing. We are working through our processes to make sure all our Afghan staff are safe.

The attack, around 480 km south of Kabul, is the latest in a string of lethal assaults in Afghanistan, many of which have targeted foreigners.

On Saturday, a suicide car bomber killed 13 troops and civilian employees of the NATO-led International Security Assistance Force (ISAF) in Kabul, including Americans, Britons and a Canadian, in the deadliest single ground attack against the coalition in 10 years of war in Afghanistan.

Four Afghans were also killed in that attack.

Senior government officials from Afghanistan, its neighbours and its Western backers will meet this week in Istanbul to discuss regional security, a meeting which is likely to be complicated by Saturday's violence.

Foreign combat troops will leave Afghanistan by the end of 2014. Violence across the country is at its worst since the start of the war 10 years ago, according to the United Nations, despite the presence of more than 130,000 foreign troops.

(Reporting by Daniel Magnowski and Mirwais Harooni; Editing by Sanjeev Miglani)