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.