Sixteen rights groups Monday urged Yemen’s Houthi rebels to end their siege of the country’s third-largest city, as the internationally recognized government said an overnight rebel attack killed at least 10 troops.

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.

The Houthis have imposed a siege on the government-held Taiz, the capital of the province by the same name, since March 2016. The southwestern city is the junction of two crucial highways: an east-west road leading to the coastal city of Mocha on the Red Sea, and another north-south, to Sanaa via Dhamar and Ibb provinces.

The joint statement said Houthi-manned checkpoints prevented residents from bringing in essential items such as fruit, vegetables, cooking gas, dialysis treatment packets, and oxygen cylinders. They also “unlawfully confiscated some of these items,” it said.

"The siege of Taiz has become nothing more than a card on the negotiating table,” said Radhya Al-Mutwakel Chairperson of Mwatana for Human Rights.

Reopening the roads of Taiz and other provinces are part of the U.N.-brokered truce between the Houthis and the internationally recognized government, which initially took effect in early April and was extended twice, the second time until early October. Both sides reported violations of the cease-fire but the truce has been the longest lull of fighting in Yemen's war, now in its eighth year.

Several rounds of U.N.-facilitated negotiations in the Jordanian capital of Amman failed to produce an agreement to ease the Houthi blockade of Taiz. In July, the rebels have rejected a U.N. proposal of a gradual reopening of Taiz roads, according to the U.N. mission in Yemen.

The internationally recognized government, meanwhile, said a Houthi attack overnight on the Dhabab area, east of Taiz city, killed at least 10 troops and wounded seven others, according to a statement carried by the official SABA news agency.

It said government troops repelled the Houthi offensive.

A spokesman for the Houthis was not immediately available for comment.

The Taiz blockade is part of Yemen’s brutal civil war since 2014, when the Houthis seized Sanaa and much of northern Yemen and forced the government into exile. A Saudi-led coalition entered the war in early 2015 to try restore the internationally recognized government to power.

The conflict has created one of the world’s worst humanitarian crises and over the years turned into a regional proxy war between Saudi Arabia and Iran. More than 150,000 people have been killed, including over 14,500 civilians.