A rocket-propelled grenade exploded in the air near a base for South Korea's aid workers and troops in Afghanistan on Sunday, but no casualties were reported, Seoul's foreign ministry said Monday.

The grenade exploded outside the base in the city of Charika in northern Afghanistan at 10:40 p.m., the ministry said. The base has come under rocket attack eight times this year, raising concerns about the safety of hundreds of South Koreans working there to reconstruct the region. South Korea has stationed some 90 aid workers and police officers as well as about 270 troops to protect them.

Sunday's attack is also the third of its kind since terrorist leader Osama bin Laden was killed in a U.S. raid in Pakistan earlier this month.

Officials are looking into the cause of the attack, according to a ministry official. They have suspected local security guards for launching the previous attacks after losing their jobs manning the base.

(Yonhap News)