An air strike killed at least 15 people at a camp for displaced people in northwest Yemen on Monday, aid workers said, as Arab warplanes bombard rebels around the country.

Doctors without Borders (MSF) said 15 bodies and 30 wounded were taken to a hospital where it operates near the Al-Mazrak camp in Hajja province.

"It was an air strike," said MSF's Middle East programme manager Pablo Marco, adding that it was likely there were more dead at the camp.

An official with the UN Office for the Coordination of Humanitarian Affairs in Yemen also said the camp had been hit.

A Saudi-led Arab coalition has been pounding rebel positions in Yemen since early Thursday.

It has vowed to keep up the raids until the Iran-backed rebels abandon their insurrection against President Abedrabbo Mansour Hadi, who has fled to Riyadh.

Warplanes carried out a fifth night of air strikes around the capital Sanaa, an AFP correspondent reported.

Positions held by the Huthi rebels and soldiers of the renegade Republican Guard overlooking the presidential palace were believed to have been targeted.

A Republican Guard camp in south Sanaa was also hit, witnesses said.

In the area around Marib, 140 kilometres (90 miles) east of Sanaa, radar facilities and surface-to-air missile batteries were targeted, local officials said.

The Huthis are backed by army units loyal to former president Ali Abdullah Saleh, who stepped down in 2012 after a year of bloody protests in the deeply tribal country, where Al-Qaeda is active.

Officials said on Monday that the ex-strongman's son had been sacked as ambassador to the United Arab Emirates, which is part of the coalition.

Ahmed Ali Saleh was relieved of his duties at the demand of the UAE, according to a Gulf diplomatic official who did not want to be named.

A Hadi aide confirmed the president had dismissed Saleh, who was appointed to the post after his father's overthrow but is believed to have remained in Yemen.

The Huthis and allied renegade military units have overrun much of Yemen and prompted Hadi to flee what had been his last remaining refuge in the main southern city Aden.

Dozens of people have been killed in several days of clashes in Aden, and Hadi's aides have said he has no immediate plan to return there.

- Chinese evacuation -

A Chinese naval flotilla, which had been carrying out anti-piracy escort missions in the Gulf of Aden and Somali waters, was sent to Yemen on Sunday to evacuate Chinese nationals, China's defence ministry said in a statement.

More than 500 Chinese citizens have been evacuated over the past two days, Beijing said.

The fighting in Yemen has stoked tensions between Sunni Arab nations and Shiite Iran.

Hadi has branded the Huthis the "puppet" of Tehran, and the prospect of an Iran-backed regime seizing the impoverished Arabian Peninsula state has alarmed its neighbours.

Israeli Prime Minister Benjamin Netanyahu warned Western powers that any nuclear deal struck in talks in the Swiss city of Lausanne would be seen as a reward for Tehran's "aggression" in Yemen.

"One cannot understand that when forces supported by Iran continue to conquer more ground in Yemen, in Lausanne they are closing their eyes to this aggression," he said in a statement

- War of words -

On Thursday, Turkish President Recep Tayyip Erdogan demanded that "Iran and the terrorist groups must withdraw" from Yemen.

He also accused Iran of meddling in other regional states, citing its role advising and coordinating Shiite militia groups in the fight against Islamic State (IS) jihadists in Iraq.

Iran said it had asked Turkey's top diplomat in Tehran to explain Erdogan's "inappropriate" remarks.

Turkey has expressed support for the Saudi-led coalition that is bombing the Huthis.

Erdogan said on Monday that he still planned to visit Iran despite a war of words with Tehran.

In Riyadh, two Saudi police officers were wounded in a drive-by shooting Sunday, the authorities said, but it was unclear if there was any link to the Yemen tensions.

"A security patrol was carrying out its duties in Riyadh when it came under fire from an unknown vehicle," a statement said.

The two were admitted to hospital and "their health situation is stable".

The attack came just days after Interior Minister Prince Mohammed bin Nayef ordered that security measures be strengthened across the kingdom.