MAAN, Jordan — Demonstrators angry with Jordan’s government have unfurled in this desert city the black battle flags of the Al Qaeda-inspired extremists now in control of large swaths of Iraq, stirring fears that support for the group is growing in Jordan.
At two rallies in Maan this past week, scores of young men, some in black masks, raised their fists, waved homemade banners bearing the logo and inscriptions of the Islamic State of Iraq and Syria.
The protesters shouted, ‘‘Down, down with Abdullah,’’ the king of Jordan. Abdullah II, a close US ally, is widely viewed as a moderate in a country considered an oasis of stability in the Middle East.
The demonstrations have been the first public displays of support for ISIS in Jordan.
Abdullah’s government has put the country’s Border Guard on alert, reinforced troops along its 125-mile frontier with Iraq and added tanks and armor to thwart any move into Jordan by the militants, who along with Sunni insurgents have seized a string of cities from northern Syria to western Iraq.
But more troubling to the Amman government than the possibility of an ISIS invasion are signs that support for the group may be expanding here and that home-grown recruits could take action in Jordan, according to former military officers, security analysts, and members of Jordan’s jihadist movement.
‘‘We no longer trust or respect the government and have been searching for an alternative that ensures our basic rights,’’ said Mohammed Kreishan, one of the marchers. ‘‘In the Islamic State, we have found our alternative.’’
Last week, antigovernment demonstrators gathered at the mosque in central Maan and marched toward the courthouse with gasoline bombs, but they were deterred by the presence of Jordanian riot police in armored personnel carriers.
A symbol of Jordan’s monarchy and central government, the charred and bullet-riddled courthouse has been the scene of near-nightly gunfire in recent weeks. ISIS banners were briefly raised on the mosque’s roof and still fly from flagpoles at traffic circles.
Maan is an impoverished regional center 150 miles south of Amman, the capital, and a world away from the five-star hotels and Western-style coffee shops of that cosmopolitan city. The official unemployment rate in Maan tops 25 percent and is far higher among its youth. One of the largest employers is a state cement factory.
Maan has been a crucible for antigovernment activists for a generation and today is home to leading Al Qaeda clerics, who themselves fear that the younger generation may no longer listen to the Salafist old guard but instead run off and join newer, more extreme groups such as ISIS.
Like most observers, Jordan’s leaders appeared to be taken by surprise by the lightning-quick advance and string of conquests this month by ISIS fighters and Sunni rebels who reached the environs of Baghdad.
Originating in Al Qaeda, patched together by splinter groups fighting in Syria and Sunni insurgents in Iraq, ISIS seeks to establish a Muslim caliphate based on an especially strict interpretation of Islamic law.
Security analysts estimate that about 2,000 Jordanians are fighting in Syria and Iraq today, at least half of them with ISIS.
Reports earlier this month suggested that ISIS forces had taken the key Iraqi-Jordanian border crossing at Turaibil, but Jordanian military officials told reporters last week that Sunni tribes control the area after the Iraqi military left after clashes with ISIS. Border traffic is lighter than normal but flowing, according to eyewitnesses.
Secretary of State John F. Kerry met with Jordan’s foreign minister, Nasser Judeh, in Paris last week to discuss a regional response to the ISIS threat.
‘‘I am worried, but I am not scared’’ of ISIS’s recent success in Iraq spilling over into Jordan, said Mohammad Farghal, director general of the Center for Strategic Studies at the King Abdullah II Defense Academy and a retired major general in Jordan’s armed forces.
‘‘We are quite confident when it comes to securing the border,’’ Farghal said. What is worrying, he said, ‘‘is that poverty and dissatisfaction create fertile ground for extremist organizations in Jordan. This is our greatest security challenge.’’