People stand at the site of a Saudi-led air strike that hit a residential area last month near Sanaa airport, May 18, 2015.

Saudi-led airstrikes targeting Yemen’s Shiite militia resumed on Monday and fierce clashes were underway across the impoverished country after a five-day truce expired.

The cease-fire had been repeatedly violated, with both the militia, known as Houthis, and Saudi-backed forces loyal to exiled Yemeni President Abdrabbu Mansour Hadi trading blame for the continued violence.

U.N. Secretary-General Ban Ki-moon hopes to convene a peace conference on Yemen in the near future, but wants the fighting to stop before he sends out invitations, his spokesman said.

U.N. deputy spokesman Farhan Haq also said Yemen’s health facilities reported higher casualties from the conflict which “are likely to be underestimates” – 1,820 people killed and 7,330 wounded since March 19. He said aid groups estimate that more than 545,000 people were displaced between March 26, when the airstrikes began, and May 7.

Dozens of politicians and tribal leaders have been holding talks in the Saudi capital to discuss a way out of the crisis, but the militia boycotted the meeting and Iran, which supports the Houthis, objected to the venue.

The coalition accuses Shiite-majority Iran of arming the Houthis as part of a larger struggle with Sunni Saudi Arabia for regional influence, something the Islamic Republic and the militia deny.

The Riyadh dialogue is set to conclude Tuesday. The Houthis reject the main aim of the talks – the restoration of Hadi, who fled the country in March in the face of militia advances – and their location in Saudi Arabia, which has been leading an air campaign against the Houthis and allied military units loyal to former President Ali Abdullah Saleh.

The truce appears to have allowed the Houthis and their allies to deploy more troops to the southern city of Aden, where there has been heavy fighting for weeks. Hadi had declared a temporary capital in there before he fled. The Houthis captured the Yemeni capital, Sanaa, last year.

The Houthis and allied forces took over the southern city of Lawdar last week, which would allow them to funnel forces into Aden from the north. Witnesses said the militia detained dozens of pro-government militiamen in Lawdar and destroyed their houses. The witnesses spoke on condition of anonymity because of security concerns. In Dhale, another gateway to Aden, pro-government militia commander Ahmed Harmel said fierce clashes raged overnight.

In Taiz, Yemen’s third largest city, street battles raged throughout the cease-fire. Medical officials there said more than 41 civilians have been killed and 230 wounded over the past month. They blamed most of the deaths on what they said was random shelling on residential areas by Houthis and allied forces.

Coalition airstrikes meanwhile struck militia positions, artillery pieces and tanks in several neighborhoods of Aden after the cease-fire expired at 11 p.m. (2000 GMT) Sunday, Yemeni security officials said. All officials spoke on condition of anonymity because they were not authorized to brief reporters.

The Houthis reported continuing airstrikes in their northern heartland of Saada near the Saudi border, which has come under heavy bombardment in recent weeks as the militia have staged cross-border attacks.

From his exile in Riyadh, Yemen’s Foreign Minister Riad Yassin told the Dubai-based Al-Arabiya network Monday that there are no ongoing talks to renew the humanitarian pause, which he said the Houthis had violated.

Also on Monday, Ali Akbar Velayati, an adviser to Iran’s supreme leader, 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 as “savage,” Velayati said the kingdom was too deeply involved in the conflict to host peace talks.

“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,” Velayati said.

Yemen is the Arab world’s poorest country, and 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.

Haq, the U.N. spokesman, said that “in the first four days of the pause humanitarian workers dispatched enough food aid to cover one month of food needs for more than 273,000 people, delivered fuel to ensure safe water access for 1.2 million and transported or distributed enough essential non-food items for nearly 32,000 people. Some 47 metric tons of medical supplies were given to hospitals and health facilities in five governorates.”

Also on Monday, Houthi official Dhaif Allah al-Shami told The Associated Press that the body of a Moroccan pilot killed when his F-16 was shot down by militia last week was flown home earlier in the day.

The pilot, identified as Yassine Bahti, is among the Moroccan forces in the Saudi-led coalition.

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