By David Shepardson

WASHINGTON, March 21 (Reuters) - The Trump administration on Tuesday imposed restrictions on carry-on electronic devices on planes coming to the United States from 10 airports in Muslim-majority countries in the Middle East and North Africa in response to unspecified terrorism threats.

The Department of Homeland Security said passengers traveling from those airports could not bring devices larger than a cellphone, such as tablets, portable DVD players, laptops and cameras, into the main cabin. Instead, they must be in checked baggage.

The new restrictions were prompted by reports that militant groups want to smuggle explosive devices in electronic gadgets, officials told reporters on a conference call on Monday.

They did not provide further details on the threat.

The airports are in Cairo; Istanbul; Kuwait City; Doha, Qatar; Casablanca, Morocco; Amman, Jordan; Riyadh and Jeddah, Saudi Arabia; and Dubai and Abu Dhabi in United Arab Emirates.

Officials said the decision had nothing to do with President Donald Trump's efforts to impose a travel ban on six majority-Muslim nations. A DHS spokeswoman said the government "did not target specific nations. We relied upon evaluated intelligence to determine which airports were affected."

On March 6, Trump signed a revised executive order barring citizens from Iran, Libya, Syria, Somalia, Sudan and Yemen from traveling to the United States for 90 days. urn:newsml:reuters.com:*:nL2N1GJ0GT Two federal judges have halted parts of the ban, saying it discriminates against Muslims. Trump has vowed to appeal up to the Supreme Court if necessary. urn:newsml:reuters.com:*:nL2N1GS0XF urn:newsml:reuters.com:*:nL2N1GT1FK

The airports affected by the electronics rules are served by nine airlines that fly directly from those cities to the United States about 50 times a day, senior government officials said.

The carriers - Royal Jordanian Airlines RJAL.AM , Egypt Air, Turkish Airlines, Saudi Arabian Airlines, Kuwait Airways KA.UL , Royal Air Maroc, Qatar Airways, Emirates and Etihad Airways - have until Friday to comply with the new policy, which took effect early on Tuesday and will be in place indefinitely.

However, an Emirates spokeswoman who confirmed the Dubai-based airline was affected by the restrictions said the new security directive would last until Oct. 14.

The policy does not affect any American carriers because none fly directly to the United States from the airports, officials said.

Officials did not explain why the restrictions only apply to travelers arriving in the United States and not for those same flights when they leave the United States.

The rules do apply to U.S. citizens traveling on those flights, but not to crew members on those foreign carriers. Homeland Security will allow passengers to use larger approved medical devices.

The agency said the procedures would "remain in place until the threat changes" and did not rule out expanding them to other airports.

DHS said in a statement it "seeks to balance risk with impacts to the traveling public and has determined that cellphones and smartphones will be allowed in accessible property at this time."

The government said it is "concerned about terrorists' ongoing interest in targeting commercial aviation, including transportation hubs over the past two years."

Reuters reported Monday that the move had been under consideration since the U.S. government learned of a threat several weeks ago.

U.S. officials have told Reuters the information gleaned from a U.S. commando raid in January in Yemen that targeted al Qaeda in the Arabian Peninsula included bombmaking techniques.

AQAP, based in Yemen, has plotted to down U.S. airliners and claimed responsibility for 2015 attack on the office of Charlie Hebdo magazine in Paris.

The group claimed responsibility for a Dec. 25, 2009, failed attempt by a Nigerian Islamist to down an airliner over Detroit. The device, hidden in the underwear of the man, Umar Farouk Abdulmutallab, failed to detonate.

In 2010, security officials in Britain and Dubai intercepted parcel bombs sent from Yemen to the United States.

The Homeland Security Department stepped up security of U.S.-bound flights in July 2014, requiring tougher screening of mobile phones and other electronic devices and requiring them to be powered up before passengers could board flights to the United States.

(Reporting by David Shepardson; Additional reporting by Yara Bayoumy, Mark Hosenball and Phil Stewart in Washington; Alexander Cornwell in Dubai and Victoria Bryan in Berlin; Editing by Lisa Shumaker and Lisa Von Ahn) ((David.Shepardson@thomsonreuters.com; 2028988324;))