DOHA (Reuters) - Yemeni army units backed by an Arab coalition attacked positions held by Houthi rebels in a strategic province east of the capital on Wednesday, a day after a U.N. envoy delivered a peace proposal to the Iran-allied fighters that control Sanaa.

A three-day ceasefire aimed at paving the way for a political settlement to Yemen's turmoil collapsed this week, and renewed fighting is threatening U.N. efforts to end a 19-month-old war.

A Saudi-led coalition launched an offensive in March last year aimed at restoring exiled president Abd-Rabbu Mansour Hadi to power and ousting the Iran-allied Houthis from their strongholds.

Yemeni forces fired artillery and dislodged Houthi fighters from towns in Marib province east of Sanaa on Wednesday, said Saudi state news agency SPA.

The Houthi group, who have controlled much of the north of the country since they ousted Hadi in 2015, said Saudi jets hit an ice factory near the port city of Mocha and houses and farms in the Serwah district of Marib on Tuesday night.

A spokesman for the Saudi-led coalition was not immediately available to comment.

Capturing Marib is important for the Saudi-led Arab coalition which aims to counter the influence of Persian-speaking Iran.

The loyalties of the province are divided. Most of its well-armed clans are allies of the Gulf states. But the Houthis, mostly members of Yemen's Zaydi Shi'ite sect, and army units loyal to former president Ali Abdullah Saleh also have friends there.

The Houthis' leader, Abdel-Malek al-Houthi, made an inpassioned speech broadcast live on social media and Lebanon's Hezbollah-run Al Manar TV station.

"You murderers and thieves, you are the corrupters of the earth with your crimes, your sieges, your killing and the damage you cause people," he said, accusing the U.S.-backed coalition of starving Yemenis by attacking them economically.

He renewed a call for the Houthis and their allies to complete the formation of a government.

U.N. special envoy Ismail Ould Cheikh visited Sanaa and presented the Houthis and their allies, the party of Saleh, with a road map addressing "security and political arrangements", the United Nations said on Tuesday, calling on both sides to extend the ceasefire and allow humanitarian aid into the country.

The Houthis said they would study the proposals.

Rajeh Badi, a spokesman for Hadi's government, told Reuters that any peace proposal must conform to previous plans for Yemen's political future: a 2011 Gulf initiative which eased Saleh from power, a 2014 national dialogue conference among political factions and a 2015 U.N. Security Council resolution calling for the Houthis to disarm and quit major cities.

"Any vision must conform to the three references," Badi said. "The government has not received any plan from the U.N. envoy or the U.N. yet."

(Reporting by Tom Finn and Noah Browning; Editing by William Maclean and Andrew Heavens)