Afghanistan is seeing a sudden rise in terrorist activity, with one bombing reported Wednesday and two failed bomb plots.
International peacekeepers say they arrested four suspected terrorists in the capital, Kabul.
A spokesman for the peacekeeping force says one of the men was found carrying a homemade explosive. He said the group is believed to be part of a terrorist cell that had been planning an attack in the city.
Remnants of Afghanistan's former Taleban government have been waging a low-level guerilla war across the country, mainly attacking government and foreign targets.
Earlier, residents in the southern province of Kandahar say a man blew himself up in an apparent accident. Witnesses say the man had been preparing a bomb inside a makeshift shelter near Kandahar city when it exploded, killing him.
Wednesday, a bombing in the same province near the border town of Spin Boldak, killed one person and injured two others. The blast occurred near a building where the provincial governor had been meeting with local officials.
Recent violence in southern Afghanistan is hampering reconstruction efforts there, including work by the United Nations.
U.N. spokesman David Singh told reporters in Kabul that the U.N. staff remains under tight security restrictions throughout southern Afghanistan.
"Missions, as far as I know, are continuing, but with armed escorts, and our staff are discouraged from going to certain areas, because that is one of the hot spots."
Despite concerns over possible terrorist strikes, U.N. and Afghan government workers say they are continuing to register voters for the country's presidential and parliamentary elections set for September.