What does Islam says about nuclear and atomic warfare? I am asking this question because some Muslim countries have such weapons. Also can we keep such weapons as deterrents?

According to the war ethics that Islam upholds a Muslim state should wage war against the combatants among the enemy only. They have no right to target innocent civilians during a war. Consequently, weapons which cause mass destruction must never be used because they result in the death of civilians.

Keeping such weapons as deterrents should also be avoided because as part of wartime ethics, it should be a declared policy of Muslim states that come what may, they would never use weapons which kill civilians.