SANAA, Yemen (AP) - A suspected U.S. drone killed four alleged al-Qaida members in Yemen on Tuesday, as the U.S. and British embassies evacuated staff amid reports of a threatened attack by al-Qaida that has triggered temporary shutdowns of 19 American diplomatic posts across the Muslim world. Yemeni officials have suggested al-Qaida threats to multiple potential targets in the Arabian Peninsula country in recent days, including foreign installations and government offices in the capital Sanaa as well as to the strategic Bab al-Mandeb straits at the entrance to the Red Sea to the south. It is not clear if these reports are the same as the intelligence that led to the embassy shutdowns, reportedly instigated by an intercepted message between al-Qaida chief Ayman al-Zawahri and his deputy in Yemen about plans for a major terror attack. The State Department on Tuesday ordered non-essential personnel at the U.S. Embassy in Yemen to leave the country. The department said in a travel warning that it had ordered the departure of non-emergency U.S. government personnel from Yemen "due to the continued potential for terrorist attacks" and said U.S. citizens in Yemen should leave immediately because of an "extremely high" security threat level. Britain's Foreign Office also said it has evacuated all staff from its embassy in Yemen due to increased security concerns. The Foreign Office said the British Embassy staff were "temporarily withdrawn to the U.K." on Tuesday. It declined to comment further. Meanwhile, there has been a spike in apparent U.S. drone strikes against al-Qaida leaders. The attack Tuesday was the fourth in two weeks. Yemen officials say the drone fired a missile at a car carrying four men in the al-Arqeen district of Marib province, setting it on fire and killing all of them. They believed that one of the dead is Saleh Jouti, a senior al-Qaida member. To the west, in the capital Sanaa, residents awoke to the sound of an aircraft buzzing overhead. Officials said it was American, and photos posted on Instagram appeared to show a P-3 Orion, a manned aircraft used for surveillance. All officials spoke anonymously as they were not authorized to brief the media. The rare overflight of the capital came shortly before the announcements of the evacuations. Yemeni authorities released the names of 25 wanted al-Qaida suspects on Monday, saying they were planning terrorist attacks in the capital, Sanaa, and other cities across the country. A statement from Yemen's Interior Ministry said the suspects were going to target foreign offices and organizations, as well as Yemeni government installations in the impoverished Arab country. It said security was beefed up around embassies, ports, airports, oil installations and power stations. Officials say potential U.S. targets in Sanaa could include the embassy and other buildings used by the United States to house personnel, as well as a military camp a few kilometers (miles) outside used by U.S. aircraft. The Yemeni statement said security forces will pay $23,000 to anyone who comes forward with information that leads to the arrests of any of the wanted men. They included allegedly senior figures in al-Qaida's Yemen branch, including Saudi nationals Ibrahim Mohammed el-Rubaish and Ibrahim Hassan el-Assiri. El-Rubaish was released from Guantanamo in 2006 and is believed to have played significant roles in al-Qaida's expanding offshoot in Yemen. He is a theological adviser to the group and his writings and sermons are prominent in the group's literature. Military officials meanwhile said the threat may be related to the Bab al-Mandeb, pointing to a visit by Defense Minister Gen. Mohammed Nasser Ahmed on Sunday to Yemeni military forces positioned at the Red Sea entrance some 276 kilometers (170 miles) south of Sanaa. Officials said that the visit came after intelligence that al-Qaida could be targeting foreign or Yemeni interests at the vital Red Sea corridor, which is a main thoroughfare for international shipping but also a crossing point of for smuggled weapons and illegal immigrants between east Africa and Yemen. Ahmed urged the forces to stay "on alert against any sabotage operations aiming at destabilizing the country," according to officials. They also spoke on condition of anonymity because they were not authorized to speak to the press. Washington considers the al-Qaida branch in Yemen to be among the terror network's most dangerous branches. The United States has also assisted Yemen's military in fighting the militants who, at one point during the country's recent political turmoil, had overrun large sections of land in the south. The group has also carried out bold assassination attacks on Yemeni security forces, killing hundreds over the past two years.