LJUBLJANA - Slovenia police on Wednesday arrested a 29-year-old man who threw a backpack over the fence of the American embassy situated at Ljubljana city center.

Related readings:  Bin Laden again unites, then divides, US and Europe  Photos show 3 dead men at bin Laden raid house  US feared Pakistan might 'alert' bin Laden  Repercussions of bin Laden's death

Police cordoned off the area soon after the incident happened at about 5 am local time. No harmful objects or substances were found when the police destroyed the backpack, the Ljubljana police administration said.

Preliminary investigations showed that the incident was "a case of a tasteless joke," the Slovenian Press Agency (STA) quoted Police Commissioner Janko Gorsek as reporting.

The arrested man, suspected of having mental disease, has been taken out of custody to be provided medical treatment, police said.

The US embassy here has been on high vigilance after al-Qaida leader Osama bin Laden, the mastermind of the 9/11 attacks in the US, was killed by US troops in the Pakistani city of Abbottabad on Sunday.

The Wednesday incident should "serve as a wake-up call that even in safe Slovenia, bad things could happen," the US embassy said in a press release.