SANA, Yemen — Yemeni security officials said Wednesday that they had foiled an audacious plot by Al Qaeda to seize an important port and kidnap or kill foreigners working there, but the claim aroused some skepticism among Yemenis and independent terrorism analysts.

The foiled plot did not appear to be related to the possible terrorist threat that has led to the closing of embassies here and elsewhere.

Yemen’s capital was in a state of high alert on Wednesday, with jet fighters soaring overhead and many streets barricaded.

Hours later, three drone strikes early Thursday east of the capital killed at least three people, according to witnesses. The strikes occurred a day after seven people were killed in a strike in the southeast portion of the country, said American government officials, who spoke on the condition of anonymity because they were not authorized to speak to reporters. A strike on Tuesday killed four people.