Do actions (kissing, touching, etc) which could lead to zina (sex before marriage) count as a major sin?

Question

People often talk of major and minor sins, minor being those which may be forgiven due to good deeds and regular prayer, etc, while major are those that one must repent for with sincerity for forgiveness.

Do touching and kissing, spending time with a girl, etc, count as major as they may directly lead to a major sin? Are the equivalent to zina. Also, could more... 'serious' acts be considered more sinful, such as kissing is worse than holding hands, and oral sex might be worse still as they are getting closer and closer to actual sex before marriage?

Does anyone know of any references in the Qur'an that refer to such acts, as I am struggling to find any, or indeed the hadith?

I understand that Allah subhanahu wa ta’ala didn't hand down a list of sins in order of how bad they are and that, at the end of the day, sin is sin, but any guidance would be appreciated.

Thank you.

Edit: This hadith seems to suggest that such actions are equivalent to zina, as the Prophet calls them "zina of the eyes", etc:

It was narrated from Abu Hurayrah that the Prophet (peace and blessings of Allaah be upon him) said: “Allaah has decreed for every son of Adam his share of zina, which he will inevitably commit. The zina of the eyes is looking, the zina of the tongue is speaking, one may wish and desire, and the private parts confirm that or deny it.”

Is this the case?

Answer 1

Lets start with touching, as that sounds like the most innocent of actions you've described in your question:

It is haraam for a man to touch the hand of a girl who is not his mahram, because the Prophet (peace and blessings of Allaah be upon him) said: “For one of you to be stabbed in the head with an iron needle is better for him than for him to touch a woman who is not permissible for him.” Narrated by al-Tabaraani from the hadeeth of Ma’qil ibn Yasaar (may Allaah have mercy on him); classed as saheeh by al-Albaani in Saheeh al-Jaami’, 5045.

Source: http://islamqa.info/en/36648

So basically, for you to die by getting stabbed in the head with an iron needle is better than touching a non mehram woman. So the most innocent of actions such as touching sounds like a pretty major sin! i.e, you're better off dying by getting an iron needle stuck in your head, than to touch a non mehram woman...

With that in mind, the other actions/activities you described could be thought of as less innocent than the "touching" action. So if touching is such a major sin, I'd hate to even try to imagine what kind of punishments would be better than those other actions.

I hope this helps you see how major the sins are for the actions you've described.