MOSCOW - A man detonated a grenade in a courthouse in Russia on Friday, killing himself and a court officer and wounding two other people, the Interfax news agency reported.Police said the unidentified assailant set off the grenade in a courthouse in the Ural Mountains city of Kurgan, 1,730 km (1,075 miles) east of Moscow, Interfax reported.The motive was unclear and there was no immediate indication of a link to Islamist insurgents who are based in Russia's North Caucasus and sometimes carry out attacks elsewhere in Russia.