Spring @Transaction not starting transactions

I am using Spring 3 with Hibernate 3. I am trying to configure Spring declarative transaction, but no matter what I try, Spring transaction is not getting started.

Here is my configuration

File: applicationContext-hibernate.xml

<tx:annotation-driven transaction-manager="txManager" />

<bean id="txManager" class="org.springframework.orm.hibernate3.HibernateTransactionManager">
<property name="sessionFactory" ref="sessionFactory" />
</bean>

<bean id="mdbDataSource" class="org.apache.commons.dbcp.BasicDataSource">
...
</bean>

<bean id="sessionFactory" class="org.springframework.orm.hibernate3.annotation.AnnotationSessionFactoryBean">
 <property name="dataSource" ref="mdbDataSource" />
  <property name="annotatedClasses">
.....
</bean>

I have a class ServiceLocatorImpl which implements ServiceLocator interface

@Service("serviceLocator")
@Transactional
public class ServiceLocatorImpl implements  ApplicationContextAware, Serializable, ServletContextAware, ServiceLocator {
public ResultObject executeService( Map objArgs )
{
      if(TransactionSynchronizationManager.isActualTransactionActive()) {
          LOGGER.debug("ServiceLocator:executeService - Active transaction found");
      } else {
        LOGGER.error("No active transaction found");
      }
         ......
}
     ....
}

It seems to me that all my configuration is correct. But when executeService method is called, TransactionSynchronizationManager.isActualTransactionActive() is always returning false.

Please help me solving this problem. Let me know if any more information required.

Update: I have wired the ServiceLocator into one of the other classes, as follows:

@Autowired
private ServiceLocator serviceLocator; // ServiceLocator is interface

I am using Spring 3.0.0 version.

executeServi