More than 60 Islamist militants tunneled out of a prison in Yemen on Wednesday in a well-executed escape that highlighted the security risks in a nation that is increasingly unstable and home to al-Qaeda’s most potent regional affiliate.

The prison break, which occurred in the eastern port city of Mukalla, was coordinated with militants attacking from the outside to divert the guards — a tactic that al-Qaeda in the Arabian Peninsula, also known as AQAP, used last summer to free prisoners in the southern city of Aden.

Among the escapees Wednesday were members of an al-Qaeda cell that has killed foreign tourists and tried to attack the U.S. Embassy in Yemen and other Western targets, according to Yemeni officials. AQAP was behind the attempted bombing of a Detroit-bound commercial flight on Christmas Day 2009 and the mailing of bombs on cargo planes destined for the United States.

The prison break could reinject committed fighters into the group’s ranks. Yemeni officials have not released a list of escapees, but one official told The Washington Post that 57 of the 62 men, many of whom fled into nearby mountains, had been convicted on terrorism charges and that some had been sentenced to death.

“Even as we don’t know exactly who escaped yet, 62 is a very worrying number,” said Barbara Bodine, a former U.S. ambassador to Yemen and a diplomat in residence at Princeton University’s Woodrow Wilson School of Public and International Affairs. “The potential for destruction and disruption is high, although AQAP’s ability to be a political force, in whatever small area they control, is very limited.”

The prison in Mukalla, which is about 300 miles east of Aden, held up to 100 convicts who were associated with al-Qaeda or who had been imprisoned after returning from Iraq, where they had joined the insurgency against the U.S.-led coalition, according to Yemeni officials. They said two Syrians and two Saudis were among those who escaped.

The inmates dug the 50-yard tunnel themselves, said one jail official, who spoke on the condition of anonymity because he was not authorized to give details of the escape.

They attacked a guard with daggers, snatched his gun and fired it as they were making their escape, the official said. One guard was fatally shot, and another was wounded. At the same time, militants attacked from the outside, and a gun battle raged for 30 minutes while the prisoners fled.

Yemen’s Interior Ministry said that three of the escapees were later killed by security forces and two were captured.

The prison break Wednesday, though far from the first in Yemen, came at a moment of political crisis in the country and seemed likely to heighten fears among U.S. counterterrorism officials that AQAP is gathering strength as the authority of the central government weakens.

President Ali Abdullah Saleh left Yemen for Saudi Arabia on June 3 after he was injured in an attack on his palace during days of bloody street fighting in the capital. Vice President Abed Rabbo Mansour Hadi has been the acting president since Saleh’s departure, and although the clashes between government loyalists and rival tribes in Sanaa have abated, the political process has stalled.

Sharply rising prices of food and gas, shortages of drinking water and long power cuts are adding to the sense of crisis. U.S. officials are eager to revive a political process that seeks to incorporate opposition groups and key tribal groups while sidelining Saleh, who insists that he will return to Yemen when his health allows.

“Obviously, the instability in Yemen is the kind that al-Qaeda feeds on or tries to take advantage, exploit, throughout the world,” State Department spokesman Mark Toner told reporters Wednesday. “It’s concerning, but our cooperation continues.”

Jeffrey Feltman, the U.S. assistant secretary of state for Near Eastern affairs, was in Sanaa on Wednesday and was scheduled to hold talks with several political figures, including Saleh’s son, who controls the country’s Republican Guard, a powerful military force.

Feltman met with Hadi and praised the acting president’s efforts to maintain a cease-fire with armed factions supporting the political opposition, according to Yemen’s state-run news agency. It said Feltman also welcomed Hadi’s efforts to open roads, remove armed government loyalists from cities, and meet with political opponents and youth movement activists.

Hadi told Feltman that he appreciated President Obama’s efforts to defuse tensions in Yemen, the agency reported. But a leading opposition group, the Organizing Committee of the Popular Youth Revolution, issued a statement denouncing Feltman’s visit and calling on anti-government activists to boycott it.

The United States has placed an array of military and intelligence assets in Yemen, including Special Operations trainers who work with Yemeni counterterrorism forces and unmanned aircraft that conduct surveillance and strike AQAP. The group’s current incarnation can be traced to a 2006 prison break in Sanaa in which its leader, Nasir al-Wuhayshi, was one of 23 escapees.

U.S. officials have said that the ongoing political chaos has hampered counterterrorism operations, and the Obama administration recently decided to expand operations to include the use of CIA-operated armed drones over Yemen. Until now, only the Joint Special Operations Command had been flying Predators to hunt for terrorists.

U.S. concern about AQAP has grown in recent weeks. Militants have seized control of Zinjibar, the capital of Abyan province, and they have been battling government troops, forcing hundreds of families to flee.

The attack on Zinjibar and another southern town by AQAP appeared to mark the first time that the underground group has attempted to take and hold territory. Some analysts caution, however, that a number of conflicting groups and interests are at play in Zinjibar.

Al-Qadhi is a special correspondent. Finn reported from Washington. Staff writer Debbi Wilgoren in Washington and correspondent Sudarsan Raghavan in Nairobi contributed to this report.