The United Nations has added three leading Huthi rebels to its list of people sanctioned in Yemen, the British mission to the world body said Wednesday.

The sanctions were imposed following persistent Huthi cross-border attacks into Saudi Arabia which have killed and wounded civilians, and the ongoing Huthi offensive on oil-rich Marib, the last loyalist stronghold in the war-torn country.

As part of the offensive, the Huthis are seeking to cut off access to humanitarian aid and are making widespread use of child soldiers, the British mission said in a statement.

The newly sanctioned are Muhammad Abd Al-Karim Al-Ghamari, who is leading the offensive; Yusuf Al-Madani, a Huthi forces leader; and Saleh Mesfer Saleh Al Shaer, an assistant defense minister who assisted in acquiring smuggled arms and weapons in violation of international humanitarian law.

The sanctions will freeze their financial assets and impose travel bans.

UNSC voices 'deep concern' over Myanmar violence

The UN Security Council expressed its "deep concern" Wednesday about recent unrest in Myanmar and called for an "immediate cessation of violence" and for efforts to ensure that civilians are not harmed.

In a statement issued as reports emerged of clashes between junta troops and fighters from a major militant group in Rakhine state, the Security Council warned that "recent developments pose particular serious challenges for the voluntary, safe, dignified, and sustainable return of Rohingya refugees and internally displaced persons."

The clashes, reported by a rebel spokesman, broke a ceasefire that had kept the peace in the western region since a February coup by the military junta.

The Southeast Asian country has been in chaos since the February putsch, with a brutal crackdown on dissent and increased fighting in borderlands involving ethnic armed organizations.

The council members also called for an "equitable, safe and unhindered delivery and distribution of Covid-19 vaccines," as well as "safe and unhindered humanitarian access to all people in need."

"They underlined that vaccines should be accessible to all and called for greater international support to ensure the availability of Covid-19 vaccines and to expedite their roll out," the statement said.

Days after the February coup, the junta reaffirmed a commitment to a ceasefire with the Arakan Army (AA), which has fought a bloody war for autonomy for Rakhine state's ethnic Rakhine population.

The ceasefire freed up military troops to battle local "self-defence forces" that have sprung up across the country in opposition to the military.

An AA spokesman told AFP Wednesday that clashes broke out after the "Myanmar military entered the area. Casualty details are not known yet."