Here are a few ways to rewrite the title in Swedish, depending on the style you prefer:

Direct translation (most accurate to the source):

Explosioner hördes i Kyiv under natten medan flyglarmet ljöd.

Alternative, more natural wording (if you want to keep the same sentence structure):

Explosioner hördes i Kyiv under natten när flyglarmet ljöd.

Punchier news-headline style:

Explosioner i Kyiv under natten – flyglarm ljöd.

All three are correct, but the first one is the most literal match to the English sentence.