SANAA, Yemen – Three al-Qaida militants were killed in a suspected U.S. drone strike in southern Yemen, Yemeni security officials said, the fourth such attack this week and a sign attacks from unmanned aircraft are on the upswing in the country.

The officials said the three men were hit as they were riding in a Land Cruiser in el-Manaseh village on the outskirts of Radda in Bayda province. Dozens of local al-Qaida-linked fighters protested the drone strikes after traditional Islamic Friday prayers.

Earlier this week another suspected U.S. drone strike killed two militants in Radda itself, Yemeni security officials say, and seven were killed in two other strikes in the southeastern province of Hadramawt. Four suspected drone strikes a week is uncommon in Yemen.

According to statistics gathered by the Long War Journal before Saturday’s attacks, the United States “is known to have carried out 41 airstrikes” this year against al-Qaida in the Arabian Peninsula, or AQAP, as the group’s branch in Yemen is known. That makes for an average of around three to four strikes per month.

The Journal, a product of the Foundation for Defense of Democracies that was founded by former U.S. officials, says that since December 2009, the CIA and the U.S. military’s Joint Special Operations Command are known to have conducted at least 54 air and missile strikes inside Yemen, excluding Saturday’s suspected attack.