Iran-allied Houthi militiamen pushed into the northeastern suburbs of the Yemeni port city of Aden Monday amid heavy clashes with loyalists of President Abed Rabbou Mansour Hadi, sources on both sides said.
Artillery and rocket fire struck the area around the Alam roundabout near the city's airport, Hadi's fighters said, after the Houthis advanced along an Arabian Sea coast road.
Aden is Hadi's last bastion of control in Yemen and remains besieged despite a fifth day of Saudi-led air trikes aimed at checking the Houthi advance.
Arab coalition warplanes had ramped up pressure on the Houthis with a fifth night of airstrikes.
The Saudi-led Sunni Arab coalition has vowed to keep up the raids until the rebels abandon their insurrection against Hadi, who has fled to Riyadh.
Fighter jets roared in the skies above Sanaa from 9 p.m. until around 5:30 a.m. Sunday, an AFP correspondent reported.
Positions held by the Houthi 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 kilometers (90 miles) east of Sanaa, radar facilities and surface-to-air missile batteries were targeted, local officials said.
In western Yemen, anti-aircraft defenses were struck in the port city of Hodeida, as well as several military positions farther south along the coast, residents said.
The Houthis 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 militants are active.
Officials said 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 Ahmed Ali Saleh, who was appointed to the post after his father's overthrow but is believed to have remained in Yemen.
The Houthis 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.
Meanwhile, a Chinese People's Liberation Army (PLA) naval detachment, which had been carrying out anti-piracy escort missions in the Gulf of Aden and Somali waters, was sent to Yemen Sunday to pull Chinese nationals from the country, China's defence ministry said in a statement.
The flotilla has two guided-missile frigates and a supply ship, Chinese media reported.
A total of 122 Chinese citizens were evacuated to Djibouti and will return to their home country from there, foreign ministry spokeswoman Hua Chunying said in Beijing.
The fighting has stoked tensions between Sunni Arab nations and Shiite Iran.
Hadi has branded the Huthis the "puppet" of Tehran, and the prospect of an Iranian-backed regime seizing the impoverished Arabian Peninsula state has alarmed its neighbors.
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 countries, citing its role advising and coordinating Shiite militia groups in the fight against ISIS jihadis in Iraq.
Iran said it had asked Turkey's top diplomat in Tehran to explain Erdogan's "inappropriate" remarks.
In the absence of its ambassador, Turkey's charge d'affaires has been "invited" to respond to "the Islamic republic's objection and regret over Erdogan's inappropriate and unusual comments," foreign ministry spokeswoman Marzieh Afkham said.
"We demand a clear and convincing response," Afkham added amid calls for Erdogan's planned visit to Tehran in early April to be canceled.
Turkey has expressed support for the Saudi-led coalition that is bombing the Houthis.
Erdogan said 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.
