ADEN (REUTERS) - Dozens of Arab special forces soldiers arrived in Aden on Sunday and deployed alongside local fighters against Yemen's Houthi militia, a militia spokesman said, signalling a major escalation of the country's war.
Saudi Arabia denied that a major ground operation was under way by the anti-Houthi coalition it leads, but declined to comment on special forces - a topic Riyadh has consistently refused to address in the more than one-month-old conflict.
In Aden, Ali al-Ahmadi, the spokesman for the Southern Popular Resistance, a group defending the southern port city against an advance by the Iranian-allied Houthis, told Reuters: "Joint land forces from the Arab coalition landed in Aden on Sunday and are now participating with the southern resistance to fight around Aden airport. "It's a limited force - 40-50 from special forces."
The coalition, which seeks to restore the government of President Abd-Rabbu Mansour Hadi, includes eight other Arab states and is receiving logistical support from the United States, Britain and France.
It has refused to rule out the eventual use of ground troops, but to date it has mostly used air power and some artillery on the Saudi border to bombard Houthi militia and allied army units.
Aden, a hotbed of anti-Houthi sentiment, has been a flashpoint since the war began on March 26, when the coalition began attacking Houthi forces opposed to Saudi-backed Hadi, who was based in Aden for several weeks before fleeing to Riyadh.
The world's top oil exporter and arch Sunni Muslim regional rival of Shi'ite Iran, Saudi Arabia says it was concerned for its own security and Yemen's stability after Shi'ite Houthi forces captured the capital and began advancing across the country, on its southern border, in September.
Fighting around Yemen has killed more than 1,000 people, including an estimated 551 civilians since the bombings started, the United Nations said on April 24.
Its children's agency UNICEF said at least 115 children were among the dead. The Saudi-led coalition attacking Yemen has probably used cluster bombs which are banned by most countries, the international monitoring group Human Rights Watch (HRW) said.
"Credible evidence indicates that the Saudi-led coalition used banned cluster munitions supplied by the United States in air strikes against Houthi forces," Human Rights Watch (HRW) said in a statement.
It said it had not been able to obtain information on possible casualties from the attacks. Saudi Arabia's coalition spokesman was not immediately available to comment on the report.
In overnight fighting, warplanes from the coalition struck Sanaa's al Dulaimi military airbase, residents of the Houthi-controlled capital said.
The aircraft also targeted a camp of forces loyal to former president Ali Abdullah Saleh, an ally of the Houthis, in Arhab district north of the city, the residents added. There was no immediate word on casualties.
In Aden, fighting continued in central Mualla and Khor Maksar districts, near the main commercial port, as well as in the city's north, around a military camp and the airport, where there have been clashes for three days, local sources said.
Iran, which backs the Houthis, does not recognise Hadi and has portrayed the air strikes as an intervention in Yemen's internal affairs.
Last week, Saudi Arabia said coalition jets destroyed the runway of Yemen's Sanaa airport to prevent an Iranian cargo plane from landing there.
Commenting on reports that the coalition had deployed troops to Aden, Brigadier General Ahmed Asseri said the alliance has not started any major ground offensive in the city.
He told Reuters there were no non-Yemeni forces fighting in Aden, but said the coalition would continue to assist local militias fighting the Houthis.
"We from the beginning said we are supporting the loyal part of the army - the loyal tribes, the loyal popular groups to protect the legitimacy of the government to protect themselves. All of these options are on the table and we use it to give those loyals the capabilities to be able to portect themselves and civilians," he said. "If some such thing happens (a special forces operation), we cannot talk about it in the media."