Yemen's powerful ex-president Ali Abdullah Saleh, a key ally of the country's dominant Houthi movement, called for an escalation of attacks against their common enemy Saudi Arabia on Sunday.
Saleh, a politician who retains influence over Yemen's military, spoke a day after an apparent Saudi-led air attack on a meeting hall in the capital Sanaa killed at least 140 people, according to local health officials cited by the United Nations.
"I call upon all the sons of this nation ... to face this aggression with all their strength and you must proceed to the battlefronts," Saleh said in a televised speech.
"The defense ministry, chairman of the joint chiefs of staff and the interior ministry must put in place the necessary measures for battle readiness at the fronts on the (Saudi) border."
Yemen ex-president urges attack on Saudi Arabia after air strike | Reuters
More than 140 people have been killed and over 500 injured in air strikes on a funeral gathering in Yemen's capital Sanaa, a senior UN official says.
Jamie McGoldrick, the UN humanitarian co-ordinator for Yemen, condemned "the horrific attack".
The rebel Houthi-run government said a Saudi-led coalition was responsible - a claim Saudi Arabia denied.
The US said it had launched an "immediate review" of its already reduced support for the coalition.
"US security co-operation with Saudi Arabia is not a blank check," White House National Security Council spokesman Ned Price said.
He said Washington was "prepared to adjust our support so as to better align with US principles, values and interests, including achieving an immediate and durable end to Yemen's tragic conflict".
The Saudi-led coalition is backing the internationally-recognised government of Yemen.
Thousands of civilians have been killed since the war began in 2014.
Mr McGoldrick said aid workers who arrived at the scene had been "shocked and outraged" by Saturday's air strikes.
He also called for an immediate investigation.
The attack targeted the funeral of the father of Houthi-appointed Interior Minister Galal al-Rawishan, an ally of the rebels and of former President Ali Abdullah Saleh.
One rescuer, Murad Tawfiq, described the scene as a "lake of blood", the Associated Press news agency reports.
Graphic photos circulating on social media show charred and mutilated bodies.
Yemen's rebel funeral hall attack 'kills scores' - BBC News