(CNN) -- Yemeni forces killed about 150 Shiite rebels Sunday in northwestern Yemen after the rebels tried to take over the presidential palace in Saada, breaching a recent cease-fire, state-run media reported.
"The Houthi fighters attacked the city from different directions with almost 70 armored vehicles, but the attack was repelled by the troops," state-run SABA reported, citing opposition party Islah's Web site.
"Two soldiers were killed and about 20 troops injured in the attack," it said.
About 70 other Houthi rebels surrendered to government forces early Sunday, SABA said.
CNN tried unsuccessfully to reach the rebels for comment.
Battles between Yemeni forces and rebels in the north have raged intermittently for five years. A government offensive launched last month escalated the bloodshed.
The conflict is considered to be both separatist, over who will assert authority in the area; and sectarian, over whether Shiite Islam will dominate in majority Sunni Yemen. The rebels are supporters of slain Shiite cleric Hussein al-Houthi.
The government said last week it would cease military operations in Yemen's northwestern regions if the rebels agreed to certain conditions, the Yemeni Embassy in Washington said. Saada, a rebel stronghold, is part of that area.
Hakim Almasmari, the editor-in-chief of The Yemen Post, told CNN on Saturday that rebel spokesman Mohammed Abdul Salam told the newspaper the rebels had agreed to the government's conditions.
On Sunday, Almasmari, citing the government and eyewitnesses, told CNN that rebels attacked the presidential palace. The Yemeni military killed 153 rebels, he said.
Once the Shiite rebels began their attack, Yemeni military helicopters were called in, Almasmari told CNN.
Also, a Yemeni official told CNN Sunday that Yemeni forces inflicted "heavy losses" on Houthi rebels in Saada after the rebels launched attacks on three military checkpoints.
Houthi Shiite rebels "took advantage" of a recent cease-fire and "executed a large-scale attack on government installations" in Saada, the Yemeni official said.
On Friday, a spokesman for the Yemeni embassy in Washington said the Yemeni military was opening an investigation into reports that an airstrike intended for the rebels had mistakenly struck and killed displaced Yemeni civilians.
Thursday's strike was meant to target Houthi rebels in Amran province, according to Yemeni government officials, who spoke on condition of anonymity.
Houthi Shiite rebels were fighting near the site, the officials said.
The government officials put the death toll at 86, while the U.N. Children's Fund, or UNICEF, said "reliable" government and media sources put the death toll at 87 -- most of them women and children.
CNN could not independently verify those numbers, and the Yemeni government did not officially comment on the airstrike.
The United Nations high commissioner for human rights, Navi Pillay, issued a statement Friday calling for an immediate and thorough investigation by Yemen's government.
There were no registered camps for internally displaced people in the region where the strike occurred, said Mohammed Albasha, the Yemen embassy spokesman.
He said there are claims from humanitarian organizations that Houthi insurgents may have used the civilians as human shields.
UNICEF issued a statement on Thursday decrying the high number of civilian casualties in the airstrike, without specifying how many civilians died.
"UNICEF is deeply concerned about reports that civilians, including children, died in an air raid on a camp for displaced persons in northern Yemen," the statement said.
The United Nations recently said fighting between Yemeni government forces and Houthi Shiite rebels in northern Yemen has displaced 150,000 people since the latest round of fighting began on August 12.
This month, the United Nations appealed for $23 million in emergency aid to help Yemenis uprooted by war, but so far it has received not a single cent.