(CNN) -- Security has been greatly tightened across Yemen as a result of intelligence that al Qaeda in the Arabian Peninsula was planning attacks in major cities, such as the capital, Sanaa, or Aden, a senior Yemeni national security official in the country told CNN Friday.
The warning comes as the U.S. State Department issued a global travel alert Friday, warning al Qaeda may launch attacks in the Middle East, North Africa and beyond in coming weeks. The U.S. government prepared to close 21 embassies and consulates in the region Sunday as a precaution.
Yemeni intelligence agencies alerted authorities of the threat two days ago, when the Yemeni president was in Washington, said the official, who spoke on condition of anonymity.
The UK Foreign Office also warned its citizens Friday against all travel to Yemen, and it strongly urged British nationals to leave now. "If you don't leave the country now while commercial carriers are still flying it is extremely unlikely that the British government will be able to evacuate you or provide consular assistance," according to the Foreign Office warning.
The steps showed heightened security concerns about intelligence that indicates a potential attack in Yemen.
According to three sources, the United States has information al Qaeda in Yemen was in the final stages of planning for an unspecified attack.
"The threat appears much worse than it has in a long time," the Yemeni official said.
Yemen has tightened security across the country, deploying security forces all major government institutions, foreign embassies, foreign residential compounds, international organizations, the official said.
According to the Yemeni official, recent U.S. drone attacks may generate reprisals.
"We take these threats seriously especially since al-Qaeda has been dealt many blows over the last few days," the official said.