DAKAR, Senegal — Islamists who have taken control of one of Africa’s most historic cities, Timbuktu, smashed the wooden door of an old mosque on Monday, continuing a campaign of destruction of religious monuments that has drawn condemnation from the United Nations and the International Criminal Court.

Two carloads of bearded men wearing turbans pulled up early Monday morning at the Sidi Yahya mosque, one of three centuries-old mosques in the city, according to several witnesses reached by telephone. Armed with axes, the men took about 40 minutes to destroy the mosque’s wooden door, the witnesses said.

Timbuktu and the rest of northern Mali are off limits to Western journalists, who have been threatened with reprisals by the Islamist groups that now control the region.

“I asked them why they were doing it,” said Cissé Baba, a high official at another of Timbuktu’s mosques who saw the destruction. “They said, ‘People believe that if that door is opened, the world will end’ ”— an un-Islamic superstition, the men explained, that had to be disproved.

“The door was on the ground,” Mr. Baba said. “It has been there for more than a century. The entire city of Timbuktu is shocked.”

Over the weekend, the Islamists of Ansar Dine — the group that has controlled Timbuktu and much of northern Mali since a coup d’état and a successful revolt against the central authority in March — destroyed at least a half-dozen above-ground mausoleums of religious leaders venerated in Timbuktu as saints. French television stations showed video of men, some armed, resolutely hacking the structures with pickaxes.

“There were about 40 of them,” said Abdoulaye Idnan, a teacher who saw the destruction. “Before they started they said, ‘Allahu akbar,’ and then they started,” he said. “People didn’t react because they are well armed. It was total silence. There were people who were crying, but what could they do?”

Ansar Dine, which means defenders of the faith, preaches a strict form of Islam that advocates a total ban on alcohol, the flogging of adulterers and the imposition of Shariah, or Islamic law, on a part of Mali that has traditionally practiced religious tolerance. The group has embarked on a campaign to stamp out what it sees as examples of decadent Western influence, and now it is going after the monuments that have symbolized Timbuktu’s eminence as a center of broad-minded Islamic teaching for centuries.

“It’s very simple: It doesn’t correspond to the rules of Islam,” said a spokesman for Ansar Dine in Timbuktu, Sanda Ould Boumana, explaining the destruction of the monuments. “This is behavior that has nothing to do with Islam.”

Asked if the destruction would continue, he said: “Of course. What doesn’t correspond to Islam, we are going to correct.”

Commenting on the censure that has come from international organizations, Mr. Boumana said: “They are not credible with us. Why doesn’t the international community interest itself in the women who are hungry here? In Timbuktu, it’s not just the dead. There are living people here. When one is Muslim, one must respect the rules of Islam. It’s about Shariah.”

An expert on Islam said Ansar Dine’s campaign of destruction corresponded to the tenets of extremist practices. “It’s not surprising at all,” said Benjamin Soares, a Mali expert at the African Studies Center in the Netherlands. “They are operating on a script, the Salafi playbook. This is something that many Muslims did in the past in other places. For them, it’s un-Islamic.”

A warning of sorts about the destruction was delivered last Friday, Mr. Idnan said, and as a result there were a number of witnesses when it began early Saturday morning.

“Friday, they told the imams it was formally forbidden to go to the cemeteries to venerate the dead, so people knew,” Mr. Idnan said.

For others in Timbuktu, this new campaign is another example of the domination of Islamist extremists, including Al Qaeda in the Islamic Maghreb, an ally of Ansar Dine, and the impotence of the Malian state and what remains of its army, still in turmoil after the March coup.

Early on Saturday, “the town woke up around its cemeteries,” said Cissé Agaly, who once ran one of the hotels that used to welcome a steady stream of tourists to the old city. “We saw the Islamists, busy destroying the mausoleums with pickaxes.”

“I am completely disillusioned,” Mr. Agaly said. “This has nothing to do with Islam. These are people without convictions. They are egoists. This is an attack on the city of Timbuktu.”