Yemen announced on Thursday that it would stop granting entry visas to travellers at the country's international airports in order to "halt terrorist infiltration," the Saba state news agency reported.
The measure comes as pressure mounts on Yemen to crack down on Al-Qaeda in the Arabian Peninsula (AQAP), which is entrenched in mountain redoubts east of the capital and claimed responsibility for the botched Christmas Day bid to down a US airliner over Detroit.
"Yemen has stopped granting visas at the airport to halt terrorist infiltration," Saba said.
Separately, a military official said that "in light of this decision, granting visas to foreigners will take place only through the embassies of Yemen, and after consulting security authorities to verify the identities of travellers."
This is to "prevent the infiltration of any suspected terrorist elements," he was quoted by the defence ministry newspaper September 26 as saying.
Six airports in Yemen receive international flights.
There was no immediate explanation as to who might be the target of the new measure, but until now very few nationalities were required to apply for visas in advance of travelling.
Earlier this week the US Senate Foreign Relations Committee released a report warning that AQAP may be training as many as three dozen US citizens who converted to Islam in prison.
The Americans traveled to Yemen upon their release, ostensibly to study Arabic, but "possibly for Al-Qaeda training," the report said, citing US law enforcement sources.
Under previous regulations, these people would have been allowed to enter the country automatically, without being previously vetted.
While "there is no public evidence of any terrorist action" by the former convicts, who may have been radicalised in prison, several have "'dropped off the radar' for weeks at a time," according to the report.
US officials "are on heightened alert because of the potential threat from extremists carrying American passports and the related challenges involved in detecting and stopping homegrown operatives," it added.
The most high-profile Yemeni-American in the country is fugitive radical imam Anwar al-Awlaqi, a native of the state of New Mexico who is now in hiding, presumably in a part of eastern Yemen where his family's tribe holds sway.
A White House aide has directly accused Awlaqi of having links with the man suspected of shooting dead 13 people at a Texas military base in November, Major Nidal Hasan.
US Homeland Security and Counterterrorism Adviser John Brennan has also said he might have had contact with the man who allegedly attempted to blow up the US airliner on December 25, Umar Farouk Abdulmutallab.
US officials are also worried about 10 non-Yemeni Americans -- "blonde-haired, blue-eyed types" -- who travelled to Yemen, converted to Islam, became fundamentalists, married Yemeni women and fit the profile of Americans that Al-Qaeda has sought to recruit.
In Washington on Wednesday, top US officials told lawmakers that Yemen's leaders had made "a decisive turn" against Al-Qaeda.
"In terms of the government of Yemen's determination and willingness to confront a threat of Al-Qaeda militants in the country, we should be and we are encouraged by recent steps the government has taken," said Jeffrey Feltman, assistant secretary of state for Near Eastern affairs..
The US State Department's top counter-terrorism official, Daniel Benjamin, told the Senate committee he had "no reason to contradict" the report and that some Yemeni institutions had proved "effective incubators of radicalisation."
But Benjamin praised "a decisive turn by the Yemeni government and a decisive interest by the international community" to help the Sanaa government battle extremism.
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