The US undertook its eighth round of airstrikes against Houthi targets in Yemen on Monday at 11.59pm local time. A Pentagon statement said the bombing was proportionate and necessary.

US military officials said the strikes were successful and had “good impacts” in all eight locations. US Central Command said the strikes were to “respond to increased Houthi destabilizing and illegal activities”.

The UK joined the airstrikes for the second time in ten days. The UK defence secretary Grant Shapps said the attacks were “in self-defence” and carried out in the interests of degrading Houthi capabilities.

A Houthi spokesman responded on X/Twitter to say the airstrikes “will only increase the Yemeni people’s determination”. Mohammed al-Bukhaiti accused the UK and US of being “perpetrators” to “genocide” in Gaza.

UK prime minister Rishi Sunak did not brief Labour leader Keir Starmer or House or Commons speaker Sir Lindsay Hoyle ahead of the strikes. Sunak was criticised 10 days ago for not informing parliament before airstrikes were carried out and this time did not brief Labour’s top team either.

The Pentagon said the operation targeted a Houthi underground storage site as well as missile and air surveillance sites. The UK ministry of defence added that it was involved in hitting multiple targets at two military sites with guided-precision bombs in the vicinity of Sana’a airfield.

The Houthi rebels, backed by Iran, have disrupted the global commercial shipping route in the Red Sea and forced ships to go around the Cape of Good Hope. The Houthis say they are acting to support Palestine amid Israel’s bombardment of Gaza, in which officials say 25,000 people have been killed, but Houthi attacks have also targeted ships with no connection to Israel.

The strikes followed a call on Monday between Sunak and US president Joe Biden. The leaders discussed further “disrupting and degrading Houthi capabilities,” a US spokesperson said.

The UK involvement on Monday appears to have been smaller than the 11 January strikes. Then, US and UK warships and jets hit more than 60 targets in 28 locations. This time, it was eight strikes, according to a joint Pentagon statement with Australia, Bahrain, Canada, the UK and Netherlands, which supported the latest military action.