What is this よう doing behind the verb?

2018-03-09 08:59:12

For full context:

https://www3.nhk.or.jp/news/html/20180306/k10011353421000.html?utm_int=news_contents_news-main_001

The sentence in question:

新燃岳で爆発的な噴火が起きたのは、7年前の平成23年以来で、気象庁は、噴火警戒レベル3を継続し、大きな噴石や火砕流に警戒するよう呼びかけています。

I would translate the part surrounding よう as "...they called out that one shall pay attention to great cinders and pyroclastic flow."

But I never saw よう used in this way.