The government said the assault, which left 10 soldiers dead and several wounded, was aimed at cutting off a key route to the blockaded city of Taiz and undermined peace efforts.
Ten Yemeni soldiers have been killed in an overnight rebel attack near the blockaded city of Taiz, Yemen's government has said, calling it a "dangerous escalation" after a months-long ceasefire.
The assault, which also left several soldiers wounded, was aimed at cutting off a key route to the southwestern city of about two million, the government said on Monday.
The Taiz attack was a "blatant challenge to all initiatives and efforts seeking to end the war and achieve peace", Yemen's internationally recognised government said in a statement.
It was "an attempt to undermine efforts to expand and extend the humanitarian truce", it added.
Yemen's warring parties have been observing a ceasefire since April, bringing a drastic reduction in hostilities, although small-scale fighting has continued.
During the overnight attack, the rebels infiltrated army sites and clashed with government soldiers in a battle fought on multiple fronts, military sources said. No detail was available on rebel casualties.
The Iran-backed Houthi rebels have blocked main roads into Taiz since 2015, the same year that a Saudi-led coalition intervened in the conflict.
READ MORE: WFP further cuts food rations in war-torn Yemen
Rights groups urge end to Taiz blockade
Also on Monday, 16 human rights groups made a joint appeal for the Houthis to open roads into Taiz to ease growing humanitarian problems in Yemen's third-biggest city.
The groups, including Human Rights Watch and Amnesty International, said in a joint statement the Houthi blockade of Taiz has severely restricted freedom of movement and impeded the flow of essential goods, medicine, and humanitarian aid to the city’s residents.
“Houthi restrictions have forced civilians to use dangerous and poorly maintained mountain roads that are the only connection between Taiz city’s besieged population and the rest of the world,” said Michael Page, deputy Middle East and North Africa director at Human Rights Watch.
"Opening the main roads would help immensely to alleviate the suffering of a population that has been in near-total isolation for seven years."
Several rounds of UN-facilitated negotiations in the Jordanian capital of Amman failed to produce an agreement to ease the Houthi blockade of Taiz.
In July, the rebels rejected a UN proposal of a gradual reopening of Taiz roads, according to the UN mission in Yemen.
The conflict in Yemen has created one of the world’s worst humanitarian crises.
More than 150,000 people have been killed, including over 14,500 civilians.
READ MORE: UN envoy aims to expand fragile truce in Yemen