Houthi rebels in civil-war torn Yemen have threatened to start attacking oil tankers and warships sailing under Saudi coalition flag, unless Riyadh lifts its naval blockade of Yemen which threatens the lives of millions in the war-torn country.

The threat of a military response to the ongoing blockade was made after Houthi leader Maj. Gen. Yousef al-Madani met leaders of the naval, coastal defense and coast guard forces Saturday. On that day, Houthi leader Abdel-Malek al-Houthi posted a message on Facebook assuring that “international navigation will remain safe as it was before,” making clear that “only those who attack our country” will be targeted.

“Battleships and oil tankers of the aggressor and its movements will not be immune from the fire of Yemeni naval forces if directed by the senior leadership,” Al Masirah news cited the country’s navy and coast guard as saying Sunday. A military spokesman for the Houthi rebels, Gen. Sharaf Ghalib Luqman, said that “systematic crimes of aggression” and the “closure of ports” compels the Houthi forces “to target all sources of funding” of the aggressor. He added the country is ready to “respond to the escalation of the Saudi-US aggression promptly.”

The Saudi-led military coalition announced last week that it was temporarily shutting all of Yemen’s land border crossings as well as its air and sea ports in response to a ballistic missile that targeted Riyadh on November 4. The kingdom accused Houthis of launching an Iran-supplied ballistic missile at the Saudi capital last weekend, and responded with bombing raids on the Yemeni capital, Sana’a. Iran has denied allegations that it supplies weapons to the Houthis, but concedes it backs the rebels’ cause. The Houthis, which are loyal to Yemen’s former president, are currently in control of most of Yemen, despite the two-year war with the Saudi Arabian-led coalition that began in defense of the exiled incumbent, Abd-Rabbu Mansour Hadi.

Following the November 6 closure of all ports of entry into Yemen, a range of UN bodies expressed concern over the fate of civilians in the country, where nearly 7 million people are starving while others depend on humanitarian assistance amidst a deadly cholera epidemic. According to the United Nations, the blockade could result in the death of millions from famine. Although Saudi Arabia says access of aid workers to the crisis-stricken country is open, aid agencies, according to Reuters, have claimed that they have not been able to enter it.

“The recent closure of the Yemen's airspace, sea and land ports has worsened the already shrinking space for the lifesaving humanitarian work. It is blocking the delivery of vital humanitarian assistance to children in desperate need in Yemen. And it is making a catastrophic situation for children far worse,” Meritxell Relano, the UNICEF Representative in Yemen said Friday. Also describing the situation in Yemen as “catastrophic,” a spokesperson for the UN Office for the Coordination of Humanitarian Affairs (OCHA) urged the Saudis to lift the blockade, as up to 90 percent of Yemen’s daily needs are served through humanitarian aid. “That lifeline has to be kept open and it is absolutely essential that the operation of the United Nations Humanitarian Air Service (UNHAS) be allowed to continue unhindered,” Jens Laerke said.

UN spokesman Stephane Dujarric warned that the Saudi-led blockade “has had a tremendously negative impact on a situation that is already catastrophic.” While Mark Lowcock, the UN under-secretary-general for humanitarian affairs, said that unless Saudi Arabia lifts the blockade, “it will be the largest famine the world has seen for many decades, with millions of victims."

Last week, the UN Security Council demanded that the Saudi-led coalition keep Yemen’s air and sea ports open to aid deliveries into the country following a session discussing Riyadh’s draconian measures.

To date, no UN warnings and threats have had any impact. The Saudi-led coalition has been waging a military campaign against Shiite Houthi rebels in Yemen since March 2015. According to the latest UN figures, the three-year-old conflict has so far claimed the lives of over 5,000 civilians, in addition to nearly 9,000 people that have been injured.