At least 10 children were killed and 21 wounded in an airstrike in northern Yemen on Saturday, aid group Doctors Without Borders has said, in an attack Houthi rebels blamed on a Saudi-led military coalition.

The airstrike hit a school in the Houthi heartland in Saada as coalition warplanes bombed multiple targets across the country. They came a week after the collapse of UN-brokered peace talks between the internationally recognized government in exile and rebels.

The airstrike on the school is likely to draw renewed condemnation of the more than year-long Saudi-led air campaign, which is supported by the United States and United Kingdom through weapons sales, intelligence and logistics support. There was no immediate comment from the coalition.

A Saudi-led coalition of Arab states intervened in Yemen in March 2015 to restore power to internationally recognized President Abed Rabbo Mansour Hadi. He was forced to flee the country after Houthi rebels and forces loyal to former President Ali Abdullah Saleh took over the capital, Sanaa, and other parts of the country in September 2014.

Despite the coalition campaign, Hadi's forces on the ground have failed to dislodge Houthis from large parts of the country, including the capital.

Houthis convene parliament

Separately on Saturday, the Houthis and Saleh loyalists convened parliament in Sanaa for the first time in nearly two years in defiance of the Saudi-based Hadi, who called the parliamentary session "invalid."

The session was attended by nearly 150 parliamentarians who approved a ruling council set up last month. According to the constitution, more than half of lawmakers must be present for a quorum. Several lawmakers have fled the country or been killed since fighting erupted, raising questions over the quorum and validity of the vote, as detailed in a tweet by Yemen-based journalist Hakim Almasmari.

The conflict has killed at least 6,400 people and displaced nearly 2.5 million, turning what was already the Arab world's poorest country into a humanitarian disaster. Nearly 80 percent of the population is in need of humanitarian assistance. The fighting has also opened up room for al-Qaeda and the so-called "Islamic State" to operate.

Saudi Arabia accuses its regional rival Iran of backing the Shiite Houthi rebels, charges they deny. Riyadh is concerned Iran is trying to carve out a sphere of influence on its border, while detractors of Saudi arguments point to real Houthi grievances and domestic factors for the conflict.

cw/cmk (AFP, AP, dpa, Reuters)