Dozens of people were wounded, including women and children, in the assault on Sanaa's residential centre.
Heavy clashes erupted in southern Yemen on Thursday while a Saudi-led coalition carried out air strikes on the capital Sanaa, leaving at least six dead in the city's residential centre, officials said.
The renewed air campaign on Sanaa — which had remained calm over the past months — came after Yemen's Iran-backed Houthi rebels, who control the capital, launched a drone attack earlier in the week on a critical oil pipeline in Saudi Arabia, Tehran's biggest rival in the region.
The Sanaa strikes targeted nine military sites in and around the city, residents said. A witness said houses had been damaged in the raids and that people lifted a body out of the rubble of one home.
The Houthi-run Al Masirah TV channel quoted the Houthi health ministry as saying six civilians, including four children, had been killed and 52 wounded, including two Russian women working in the health sector.
A coalition spokesman did not immediately respond to a request for comment.
A coalition statement carried by Saudi-owned Al Arabiya TV said the alliance struck military bases and facilities and weapons storage sites with the aim of "neutralising the ability of the Houthi militia to carry out acts of aggression".
"The sorties achieved its goals with full precision," the coalition said. It had urged civilians to avoid those targets.
One resident reported a strike near a densely-populated district and said ambulances rushed to the area, where flames and clouds of smoke could be seen.
"There was an air strike near us, in the middle of an area packed with residents between Hael and Raqas (streets)," Abdulrazaq Mohammed said.
"The explosion was so strong that stones were flying. This is the first time our house shakes so much."
The coalition has previously targeted suspected drone and missile storage sites in the city.
Is Yemen's war expanding?
Yemen has been embroiled in a civil war pitting the Houthis against the government of President Abd Rabbu Mansour Hadi, backed by the Saudi-led coalition, since March 2015.
The Houthis have been pushing to gain more territory from coalition-backed government forces in the country's southern Dhale governorate.
Yemen's human rights minister, Mohammed Askar, told reporters on Thursday that weeks-long fighting in Dhale has killed over 27 civilians and displaced around 10,000 people.
The Sanaa air strikes and renewed fighting in Yemen's Hudaida port that breached a UN-sponsored truce in the Red Sea city could complicate peace efforts to end the four-year war that has killed tens of thousands of people, many of them civilians, and pushed the country to the brink of famine.
The coalition receives arms and intelligence from Western nations to try to restore Hadi's government, now based in the southern port of Aden.
The conflict is widely seen in the region as a proxy war between Saudi Arabia and Iran.
The Houthis deny being puppets of Tehran and say their revolution is against corruption.
Saudi Arabia's deputy defence minister on Thursday accused Iran of ordering the attack on the Saudi oil installations, which the Houthis had claimed. The attack "proves that these militias are merely a tool that Iran's regime uses to implement its expansionist agenda," tweeted Prince Khalid bin Salman, a son of King Salman.
Other Saudi officials fired off similar tweets, ratcheting up pressure on the kingdom's regional arch-enemy amid heightened tension between Washington and Tehran over sanctions and US military presence in the Gulf.
"The Houthis are an integral part of the Revolutionary Guard forces of Iran and follow their orders, as proven by them targeting installations in the kingdom," Minister of State for Foreign Affairs Adel al Jubeir tweeted.
The ambassador to Yemen followed up, writing that the Houthis had "made Yemen a platform for Iranian terrorism against Yemenis and their interests, and a tool to attack Saudi Arabia."
Hudaida and the ceasefire
The warring parties agreed to last December at UN-sponsored peace talks in Sweden on a ceasefire and troop withdrawal deal in Hudaida, a lifeline for millions of Yemenis that became the focus of the war last year.
The pact, the first major breakthrough in over four years, stalled for months amid deep suspicion among all parties, but special envoy Martin Griffiths secured some progress when the Houthis started withdrawing from three ports last Saturday.
Pro-coalition troops are expected to pull back as well under the deal once the two sides work out details for a broader phase two redeployment in Hudaida, the main entry point for Yemen's commercial and aid imports and the Houthis' key supply line.
Saudi Arabia and the UAE accuse the group of smuggling Iranian weapons, including missiles that have been launched at Saudi cities.
The Houthis and Tehran deny the accusations.