It is haram (forbidden) for a non-mahram man and a non-mahram woman to seek any kind of pleasures from each other (it is even forbidden for them to cast lustful look at each other). It is for the same reason that, according to Islam, it is not permissible for a man to be alone with a non-mahram woman so that they may not fall into a sin. Therefore, it is haram for a man to hug or to touch a non-mahram woman with lust and with the intention of deriving sexual pleasure but there is no punishment for it. However, an Islamic ruler can punish those who have committed such a haram act (by putting them into a jail). Also, if a woman has been teased or physically abused by a non-mahram man, she can complain against him. In case a man and a woman have committed a sin due to ignorance and temptations and no one other than God has witnessed them commit the sin, they should not turn themselves in to the Islamic ruler; it is not permissible for them to reveal their secrets to anyone and to damage their reputation. In fact, to regret over their past and repent to God sincerely would be sufficient. Man should always be hopeful of God's mercy and forgiveness because God accepts repentance and He loves those who repent.
 - Tawzih al-Masail (with annotation by Imam Khomeini), vol.1, pg. 497, Issue No.889.