ANKARA (Reuters) - Turkish security forces have killed 21 Kurdistan Workers Party (PKK) rebels in fighting in the southeast of the country for the loss of three soldiers, state-run Anatolian news agency said on Thursday. It said 10 of the guerrillas were killed in Diyarbakir province, six of them in Siirt, three in Mardin and two in Bingol. It did not say when the deaths took place. Ten civilians kidnapped by the PKK were also released during the operations, the agency said. More than 27,000 people have been killed in the 13-year conflict between Turkish security forces and the PKK who are fighting for self-rule in the mainly Kurdish southeast.