Osamh Abdulrhman, AP
A destroyed vehicle is seen at the site of a bomb attack in Sanaa, Yemen, Wednesday, June 17, 2015. Two suicide bombers and another blast targeted the headquarters of Yemen's Shiite rebels in the capital, killing several people and wounding some 60 others, officials said.

SANAA, Yemen — Two suicide bombers and another blast targeted the headquarters of Yemen's Shiite rebels in the capital, Sanaa, on Wednesday, killing at least four people and wounding some 60 others, officials said. Earlier Saudi-led airstrikes hit a convoy of civilian vehicles and killed at least 31 people, authorities said.

The Health Ministry said in a statement that the casualty figure from the Sanaa attacks on Wednesday night was "preliminary," as Muslims around the world prepared for the start of the holy month of Ramadan. Ambulances rushed through the streets in northern and central parts of the capital where the offices of the rebels, known as Houthis, are located.

Security officials said two suicide attackers drove car bombs into the gates of two buildings before detonating them. They said a third attack targeted a gathering of Houthis in Sanaa's Green Dome district.

Yemen's conflict pits the Houthis — who seized the capital last year — and military units loyal to former President Ali Abdullah Saleh against an array of forces, including southern separatists, local and tribal militias, Islamic militants and loyalists of exiled President Abed Rabbo Mansour Hadi. The Saudi-led coalition backing Hadi began carrying out airstrikes on March 26.

The Arab world's poorest nation is also home of the world's most dangerous al-Qaida offshoot. The group, whose leader was killed in a U.S. drone strike last week, has targeted the Houthis in dozens of deadly attacks and its militants are engaged in near-daily attacks in central Yemen.

U.N.-brokered talks between the rival factions are underway in Geneva, aimed at ending the violence and addressing the humanitarian crisis in Yemen. Mediators hope for a humanitarian truce during Ramadan, which starts Thursday, but neither side has shown any desire to compromise.

The earlier Saudi-led airstrikes struck a convoy of civilian vehicles fleeing north from the southern city of Aden, which has seen intense fighting. Medics described a scene of carnage, with body parts scattered across the highway and smoke billowing from charred vehicles. They said at least 31 people were killed.

Despite nearly three months of airstrikes, anti-Houthi forces have made little progress. The violence has killed at least 1,412 civilians and wounded 3,423, according to the United Nations.

Heavy fighting also was underway Wednesday in the oil and gas-rich Marib province east of the capital, Sanaa, where Sunni tribes have fended off a number of Houthi advances on the city of al-Saheel, security officials said. Airstrikes targeted the Houthis in Marib as well as in Sanaa, Aden, the rebels' northern heartland and the western city of Taiz, they said.

In Taiz, Houthi shelling has killed more than 30 civilians in the past 48 hours, medical officials and witnesses said. The rebels control a third of the city.

All officials spoke on condition of anonymity as they were not authorized to speak to journalists.

In a country already suffering from shortages of fuel, water and medical supplies, the fighting endangers hospital as well. A report released Wednesday by Human Rights Watch accused the Houthis and their rivals of turning a main hospital in Aden called al-Jumhouria into a warzone.

In one incident April 19, the group said hundreds of southern fighters forced staffers to locate wounded Houthis receiving treatment there. Human Rights Watch says at least two of the wounded were shot dead outside the hospital.

"The fighting in Yemen is terrible enough without both sides bringing the battle into hospitals," said Joe Stork, deputy Middle East and North Africa director at Human Rights Watch.