KABUL, Afghanistan – A plane crashed in southern Afghanistan on Saturday, killing four international service members on the same day the Taliban said they were gearing up to launch their spring offensive with attacks on military and diplomatic targets.

Initial reporting indicated there was no enemy activity in the area where the plane went down, the NATO-led coalition said in a statement confirming the crash. Coalition personnel secured the site and were investigating the cause of the crash.

The brief statement did not identify the nationalities of the victims, or say exactly where the crash occurred.

However, Mohammad Jan Rasoulyar, deputy governor of the southern province of Zabul, said an aircraft belonging to foreign forces crashed Saturday afternoon in Shah Joy district.

The spring Taliban offensive, which is to begin on Sunday, comes as U.S.-backed efforts to try to reconcile the Islamic militant movement with the Afghan government have so far failed.

Insurgents already have stepped up attacks this spring as they try to position themselves for power ahead of national elections and the planned withdrawal of most U.S. and other foreign combat troops by the end of 2014.

The Afghan Defense Ministry said its security forces are prepared for Taliban’s new campaign. “The Afghan National Army is ready to neutralize the offensive,” the ministry said, adding that the soldiers now have the support and trust of many Afghans.

The Taliban’s leadership vowed on Saturday that “every possible tactic will be utilized in order to detain or inflict heavy casualties on the foreign transgressors” during its spring offensive.

In a sign of Taliban’s determination to replace Afghanistan’s government with one promoting a stricter interpretation of Islamic law, the insurgents named the new offensive after a legendary Muslim military commander, Khalid ibn al-Walid. Also known as the “Drawn Sword of God,” he was a companion of Islam’s Prophet Muhammad.

The Taliban threatened to infiltrate the Afghan security forces and conduct more attacks on Afghan policemen and soldiers as well as foreign troops. Such attacks threaten the strength of the Afghan forces as they work to take over responsibility from international troops. The latest one occurred in March, when a member of Afghanistan’s government-backed village defense program shot and killed five of his colleagues in Badghis province in northwest Afghanistan

April has already been the worst month for combat deaths so far this year. According to an Associated Press tally, 257 people — including civilians, Afghan security forces and foreign troops — have been killed in violence around the nation. April has already been the worst month for combat deaths so far this year. According to an Associated Press tally, 257 people — including civilians, Afghan security forces and foreign troops — have been killed in violence around the nation. During that time 217 insurgents have died.

Last year during April, 179 civilians, foreign troops and Afghan security forces, plus 268 insurgents, were killed.

Still, U.S. Marine Gen. Joseph Dunford, the top commander of U.S. and NATO forces in Afghanistan, said Wednesday that the security situation had improved across the country, with Afghan forces now leading 80 percent of all conventional operations.

Elsewhere in Afghanistan, the Taliban late Friday freed nine civilian de-miners it had captured in Kandahar province after talks involving tribal elders, spokesman Javeed Faisal said.