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DUBLIN (AP) — Northern Ireland police discovered a suspected mortar Friday that was aimed at one of Belfast's biggest police bases in an apparent escalation of Irish Republican Army efforts to target British security forces.

Dozens of homes were evacuated, two primary schools were closed and a funeral ceremony had to be relocated as British army explosives experts used two remote-controlled robots to examine the suspicious tube. A second robot had to be deployed as the first, trying to inspect the device partly concealed in uneven grassy ground, was tipped on its side by gusting winds.

The Police Service of Northern Ireland said it wasn't certain yet whether the tube contained a viable round. No group claimed responsibility. Police and politicians blamed IRA die-hards who reject the cease-fire observed since 1997 by the dominant faction, the Provisional IRA.

In recent months, today's IRA activists have repeatedly attempted to use Provisional IRA-style mortars to blast police vehicles and bases, but so far all their efforts have failed. Police usually have seized the homemade weapons before they could be fired, reflecting their close surveillance of the extremists.

On March 3, police in Northern Ireland's second-largest city, Londonderry, caught two men trying to drive a four-tube mortar weapon into the city for likely deployment against its main police station.

Friday's suspected mortar system was put into the ground with its lone tube pointing toward New Barnsley police station, the biggest security installation in west Belfast with bomb-resistant watchtowers and high brick walls. The base, built in the mid-1990s and designed to withstand large car bombs, forms part of a so-called "peace line" of walls that have separated rival Irish Catholic and British Protestant districts in the area since the early 1970s.

Reflecting the divisions of the area, Protestant evacuees from the security alert sheltered in a nearby Presbyterian church, while the Catholic side took refuge in a community hall more than a mile (2 kilometers) away.

The Provisional IRA killed nearly 1,800 people during a failed 1970-1997 campaign to force Northern Ireland out of the United Kingdom. Its mortar designs were particularly deadly and were copied by guerrilla movements worldwide. But it has officially ceased to exist since renouncing violence and disarming in 2005.

Security chiefs estimate that at least 300 militants, including dozens of former Provisionals, continue to pursue sporadic bombings and shootings. They have used a panoply of names in the past, but since mid-2012 most of the factions' leaders have come together under a single banner and insist that their organization should be called simply the IRA. One faction called the Continuity IRA has retained its nom de guerre.

Today's IRA hopes to ape the success of the Provisionals. Their weapons engineers' biggest vehicle-mounted mortars were nicknamed "barrack busters," while horizontally fired mortars placed by roadsides fired armor-piercing rounds into passing police and army vehicles.

In 1985, a mortar attack on a police base in the border town of Newry killed nine officers dining in the base's cafeteria — the worst single slaying of officers from the entire Northern Ireland conflict.

In 1991, the Provisionals fired three mortar shells into the backyard of Downing Street, the official London residence of the British prime minister, during a Cabinet meeting. Only one round detonated, shattering windows but injuring nobody.

In 1994, mortar attacks on the runways of Heathrow Airport shut down Europe's busiest air hub. The Provisional IRA had placed the timer-triggered weapons in vehicles in parking lots days beforehand.