directory_country_region

public function getcitiesAction()
{
    if (!$this->getRequest()->isXmlHttpRequest()) {
        return;
    }

    $regionId = (int)$this->getRequest()->getParam('region_id');
    $countryId = $this->getRequest()->getParam('country_id');

    if (!$regionId || !$countryId) {
        return;
    }

    echo Mage::helper('your data helper')->getCities($countryId, $regionId);

    return;
}

 public function getLocalityAction()
{
    if (!$this->getRequest()->isXmlHttpRequest()) {
        return;
    }

    $cityId = (int)$this->getRequest()->getParam('city_id');


    if (!cityId ) {
        return;
    }

    echo Mage::helper('your data helper')->getlocalities($cityId);

    return;
}

public function getCities($countryId, $regionId)
{
    $cityCollection = Mage::getModel('your city model')->getCollection();
        $cityCollection->addFieldToSelect('cityname')
        ->addFieldToFilter('country_id', $countryId)
        ->addFieldToFilter('region_id', $regionId);

    $jsonData = Mage::helper('core')->jsonEncode($cityCollection->getData());

    return $jsonData;
}


public function getlocalities($cityId)
{
    $localityCollection = Mage::getModel('your locality model')->getCollection();
        $cityCollection->addFieldToSelect('locality_name')
        ->addFieldToFilter('city_id', $cityId)


    $jsonData = Mage::helper('core')->jsonEncode($localityCollection ->getData());

    return $jsonData;
}