Airstrikes by the United States and United Kingdom against Yemen's Houthi militia violate international laws as well as Yemen's sovereignty, and risk sparking a broader regional conflict, contrary to their claimed goals and international de-escalation efforts, experts said.

The US-UK attacks on Houthi targets in Sanaa and other areas of Yemen on Friday killed five people while injuring six, Houthi spokesman Yahya Sarea said in a statement.

On Sunday, the allies conducted another strike on the Red Sea port city of Hodeidah, the Houthi-run al-Masirah TV reported.

While the US claimed the strikes were "necessary and proportionate" against Houthi attacks on commercial ships in the Red Sea, as US Ambassador Linda Thomas-Greenfield told the United Nations, the Houthis warned that the West's "aggression" will not go unanswered and unpunished, Xinhua News Agency reported. A number of countries have criticized the US-UK strikes.

Abdalfatah Asqool, an international law lecturer at the University of Palestine, told China Daily the US-UK strikes are illegal because there is no international legal cover for these strikes, such as a decision made by the UN Security Council.

"Thus, these attacks, according to international law, are considered a violation of the sovereignty of Yemen," Asqool said.

Despite US calls to avoid an escalation of the conflict and aggression against the Gaza Strip, its practices "prove the opposite "at the same time, he said.

On Monday, a missile attack targeted a commercial ship in the Gulf of Aden off the coast of Yemen. The US Central Command confirmed the attack on X, formerly Twitter, saying: "Houthi militants fired an anti-ship ballistic missile from Houthi-controlled areas of Yemen and struck the M/V Gibraltar Eagle, a Marshall Islands-flagged, US-owned and operated container ship."

After the Western strikes last week, the Houthis said they would not be deterred and declared that US and British interests were "legitimate targets".

"When the US and the UK strike Yemen, they are not only expanding the conflict — they are also violating international law. As the Houthi practices in the Red Sea do not affect the US or the UK interests or even the freedom of navigation, it only aims at putting pressure on Israel to stop the massacres against Palestinians and force Israel to allow humanitarian aid to enter the Gaza Strip," Asqool said.

Therefore, the easiest solution to stop the Houthi operations is to let humanitarian aid enter the Gaza Strip and stop the conflict, he said.

While Iran and Russia led a group of countries in condemning the US-led strikes, Turkish President Recep Tayyip Erdogan criticized the strikes as a "disproportionate use of force", accusing the US-led forces of seeking to turn the Red Sea into a "bloodbath", reported the Hurriyet Daily News.

UN Secretary-General Antonio Guterres appealed to countries to avoid an escalation in the Red Sea, saying it endangers the safety and security of global supply chains and hurts the economic and humanitarian situation worldwide.

Khaldoon Abdulla, a nonresident fellow at the Asia Middle East Center for Research and Dialogue, said the US this time was inclined to take more severe steps, calling for an alliance and military actions, which "raises the question about the duality of the responses".

He also said that given the fact the connectivity of supply chains and transshipment along ports, the Houthi's operation against ships sailing to Israel might have an impact on international shipping, but it is relatively small, compared to piracy activities near other strategic maritime routes such as the Malacca Strait.

"Therefore, the disproportioned response of the US, its allies and shipping companies raises a question about the real objectives of those measurements," Abdulla said.