Yemen's Houthi group hit a Saudi oil tanker off the main port city of Hodeidah on Tuesday, the Saudi-led coalition said, in an attack that could complicate a new United Nations push to end a war that has killed more than 10,000 people.
The Iranian-aligned Houthis said they had targeted a coalition warship in response to an air strike on Hodeidah on Monday that killed at least a dozen civilians, including seven children.
Tensions have been rising in recent days after the Houthis, who control most of northern Yemen, launched a series of missile strikes on Saudi Arabia, including the capital Riyadh, in recent days.
In a statement carried by Saudi media, the coalition said the oil tanker was in international waters when it came under "Houthi-Iranian attack" at around 1330 local time (1030 GMT).
A coalition warship conducted a "swift intervention" foiling the attack, it said, without identifying the type of weapon used in the assault. "As a result of that attack, the tanker was subjected to a slight but ineffective hit and it resumed its naval course northwards, escorted by a coalition warship," the statement said.
A European Union naval force that operates in the region confirmed the ship was underway, adding that the crew were safe and unharmed.
The media department of the Houthi-run Yemeni military said naval forces had "targeted a battleship belonging to the coalition in response to the bombardment of displaced people in Hodeidah". It gave no further details.
The department's text message was referring to an air strike by the Saudi-led coalition on Monday in Houthi-controlled Hodeidah that destroyed a house and killed 12 civilians from the same family, including seven children.
A coalition spokesman said the alliance takes the report very seriously, promising a full investigation.
Last week, Saudi air defences intercepted a flurry of missiles, and falling debris caused the first death in the capital Riyadh.
Saudi Arabia accuses Iran of supplying missiles to the Houthis, who have taken over the Yemeni capital Sanaa and other parts of the country. Tehran and the Houthis deny the charge.
CALL FOR ENDING WAR
Earlier on Tuesday, U.N. Secretary-General Antonio Guterres urged the warring sides in Yemen to reach a political settlement to end a conflict now in its fourth year that has left 22 million people in urgent need of aid.
Speaking in Geneva on the sidelines of a U.N. pledging conference for Yemen, Guterres said his Special Envoy Martin Griffiths will head to the United Arab Emirates, Oman and the Yemeni government-held city of Aden in the drive for peace, Guterres told reporters.
Griffiths has already held talks with Houthi authorities as well as internationally-recognised Yemeni President Abd-Rabbu Mansour Hadi and Saudi officials in Riyadh.
Guterres said he saw "positive perspectives" for preparing a plan of action "to lead to an effective inter-Yemeni dialogue able to achieve a political solution, with of course the involvement of all those that are relevant in this conflict".
"I am optimistic about that possibility," the United Nations chief added.
He announced that more than $2 billion has been pledged towards a U.N. humanitarian appeal of $3 billion for Yemen this year. It includes $930 million from Saudi Arabia and the UAE which lead the coalition air strikes.
Yemeni Foreign Minister Abdel-Malek al-Mekhlafi called for a return to the negotiating table to end the war in the Arabian peninsula's poorest country and said his government was working to open blockaded ports and airports to aid.