ATHENS, Greece (AP) — Greek police clashed with shipyard workers protesting pay arrears Thursday after they broke into the Defense Ministry grounds, while hundreds of farmers on tractors tried to invade the country's second-busiest airport on Crete during an anti-austerity protest.

Greece has been gripped by a severe financial crisis since late 2009, and waves of spending cuts and tax hikes have led to frequent strikes and demonstrations. The nation's 3-month-old coalition government is currently preparing a major new austerity package demanded by rescue creditors.

Unions have promised new protests and a general strike next week when the government's new €13.5 billion ($17.5 billion) program is debated in parliament — where the conservative-led coalition controls enough seats to pass the measures.

In Athens on Thursday, more than 100 protesters forced open the shuttered entrance to the Defense Ministry complex, crossing the courtyard and blocking the entrance to the general staff building. Riot police were called in to force back the demonstrators, who were demanding to meet with ministry officials.

Greece's top military officer, Gen. Michalis Kostarakos, was heckled by the shipyard workers when he came out to speak to them by using their portable loudspeaker. "First get off my base," Kostarakos told the protesters, arguing that the military had no part in the workers' dispute with the government.

Police said 106 people were detained for questioning, prompting another protest gathering outside police headquarters. Riot police used pepper spray to prevent a group of protesters from barging into the building.

Workers from the Skaramangas Shipyards, which deals mainly with military contacts, say they have not been paid in months. Scuffles broke out as protesters tried to push through the police cordon protecting the entrance to the main building.

On the southern island of Crete, hundreds of farmers taking part in an anti-austerity protest on Thursday tried to invade the terminal and the runway of Iraklio airport. Police kept them off with tear gas, and one man was detained for trying to drive his tractor onto the runway.

Airport authorities said flights were not affected by the protest. Crete is a major tourist destination, attracting more than 44,000 flights last year.

Finance Minister Yannis Stournaras said Wednesday there were still considerable differences between the government and Greece's debt inspectors from the International Monetary Fund, European Commission and European Central Bank over the new austerity package. But he said he hopes to clinch a deal by next week.

The country has been in recession since 2008, and the total contraction is projected to reach a cumulative 25 percent at the end of next year.