Israel has severely weakened Hamas and Hezbollah. Now it's going after another member of Iran's so-called axis of resistance: the Houthi rebels of Yemen.

The head of the World Health Organization said he was about to board a flight in the Yemeni capital when the airport came under bombardment.

World Health Organization chief Tedros Adhanom Ghebreyesus was about to board a plane at the Sanaa International Airport when it came under attack. A crew member on the plane was injured, he said.

Israel launched a series of airstrikes Thursday against targets inside Yemen. Israeli military officials said the targeted locations are controlled by Iran-backed Houthi rebels who have repeatedly attacked Israeli territory with drones and surface-to-surface missiles over the past several days.

Israel is signaling a wider campaign against Houthi militants in Yemen, a mountainous and impoverished country more than 1,000 miles from Israeli territory.

Israel struck multiple targets in Yemen it said were controlled by Houthis, the last of the Iran-backed groups still fully engaged in the regional war that began 14 months ago.

The strikes come as Israelis endure continued rocket attacks from the Houthi militia in Yemen even as attacks from Hezbollah in Lebanon and Hamas in the Gaza Strip have diminished.