(Adds U.S. coast guard statement)
DOHA, March 26 (Reuters) - Yemen shut its major seaports on Thursday, industry and local sources said, after neighbouring Saudi Arabia and Arab allies launched air strikes against Iran-allied Houthi forces fighting Yemen's Western-backed president.
Warplanes bombed sites near Houthi-held capital Sanaa and their positions near the Saudi border. In the south, Houthis and army loyalists battled with militiamen loyal to Yemeni President Abd-Rabbu Mansour Hadi near the port city of Aden.
"All major seaports were shut down on Thursday due to the rising conflict," said an industry source. Local sources in Yemen confirmed the closure.
The U.S. coast guard issued restrictions on some vessels arriving into the United States from a number of Yemeni ports that "do not maintain effective anti-terrorism measures", according to a statement.
Yemen exports about 1.4-1.5 million barrels of Masila crude each month, mainly to China.
The ports closed include Aden, Al Mukalla, Al Mokha and Al Hudaydah, the sources said, giving no further details.
"It looks like no one is working at the ports across Yemen today," a shipping industry source told Reuters.
On Wednesday, public sector workers in Aden were instructed to return home and some residents armed themselves as the conflict between Hadi's supporters and the Houthis and their allies came to a head.
The U.S. coast guard said conditions of entry would be imposed on vessels arriving from al-Shehr and Al Hudaydah.
"The 2012 exception remains in place for vessels arriving from the Balhaf LNG," it added.
The majority of Yemen's oil production is located in the north of the country, while the rest comes from the southern area of Shabwa.
French oil company Total is the biggest foreign investor in Yemen and operates the Balhaf gas export facility, which mainly exports natural gas to Asia and Europe.
(Reporting by Amena Bakr in Doha, Mohamed Ghobari in Cairo, Jonathan Saul in London and Reem Shamseddine in Khobar; editing by David Clarke, Jason Neely and David Evans)