Saudi-led coalition airstrikes targeting Yemen's Shiite rebels resumed early on Monday in the southern port city of Aden after a five-day truce expired amid talks on the war-torn country's future that were boycotted by the rebels.

Even while it was in effect, the cease-fire had not halted all the fighting in Yemen between the rebels, known as Houthis, and government forces loyal to exiled Yemeni President Abed Rabbo Mansour Hadi.

Meanwhile, the three-days of talks on Yemen's future saw hundreds of politicians and tribal leaders gather in the Saudi capital. The meeting was boycotted by the rebels and their Iranian backers voiced objections to the venue of the talks.

Western countries accuse Shiite power Iran of backing the Houthi rebels, something the Islamic Republic and the rebels deny. The absence of the Houthis at the conference in Riyadh, which is to end Tuesday, means the dialogue is unlikely to end the violence.

The Shiite rebels reject the main aim of the talks -- the restoration of Hadi, who fled the country in March in the face of rebel advances -- and the location of the negotiations in Saudi Arabia, which is leading an air campaign against the Houthis and their allies.

Coalition airstrikes hit rebel positions and tanks in several neighborhoods of Aden after the cease-fire expired at 11 p.m. on Sunday, Yemeni security officials said, speaking on condition of anonymity because they were not authorized to speak to the media.

From his exile in Riyadh, Yemen's Foreign Minister Riad Yassin said Monday that there are no ongoing talks to renew the humanitarian pause which he said Shiite rebels, also known as Houthis, have violated. He spoke to the Dubai-based Al-Arabiya network.

Also on Monday, Ali Akbar Velayati, an adviser to Iran's Supreme Leader Ayatollah Ali Khamenei, told reporters during a visit to Beirut that a dialogue on Yemen should be mediated by an international organization, such as the United Nations, and held in a "neutral country."

Describing the Saudi-led airstrikes against Houthis in Yemen as "savage," Velayati said that the kingdom was too deeply involved in the conflict with its airstrikes campaign to host peace talks.

Saudi Arabia is "part of the conflict so it cannot host a conference on solving the Yemeni crisis," the Iranian official said. "A national dialogue should be held ...  in a neutral country that has no links to Riyadh or other sides who are part of the conflict."

Since late March, Saudi Arabia has led the campaign against the Houthis and allied military units loyal to former President Ali Abdullah Saleh. The campaign is aimed at weakening the Houthis and restoring Hadi, who spoke at the conference in Riyadh on Sunday.

Yemen's conflict has killed more than 1,400 people -- many of them civilians -- since March 19, according to the U.N. The country of some 25 million people has endured shortages of food, water, medicine and electricity as a result of a Saudi-led blockade. Humanitarian organizations had been scrambling to distribute aid before the end of the truce.