KABUL: A top Taliban commander warned Wednesday that militants would unleash a wave of ambushes, roadside bombs and suicide attacks in a new spring offensive. In a possible foreshadowing of coming violence, coalition and Afghan troops killed 42 militants in three operations, officials said.

Mullah Berader, a top deputy to Taliban leader Mullah Omar, said the Taliban plan to launch a new offensive Thursday against international and Afghan troops, government officials and "whoever is supporting invaders in our country."

Taliban militants have increased attacks in the last three years after what appeared to be an initial defeat of the radical Islamist regime, which was toppled by the 2001 U.S.-led invasion. President Barack Obama has ordered 21,000 additional U.S. troops to the country to bolster the record 38,000 American forces already in the country.

"As American and NATO countries plan to send more troops to Afghanistan, it is necessary for the Afghans and Afghan mujahedeen to defend their country," militant spokesman Zabiullah Mujahid told The Associated Press in a statement he attributed to Berader.

Taliban commanders in the past have made boasts of impending violence — such as hundreds or thousands of suicide bombers waiting to attack around the country — that never materialized. But Berader's comparatively measured threat could signal a start point to more aggressive attacks this year.

With so many more American forces deploying to Afghanistan, U.S. commanders have said they expect violence to rise across the country this summer, when Taliban attacks typically reach their pinnacle.

In the latest series of battles, coalition and Afghan forces killed 42 militants Wednesday in three clashes.

Though there were no casualties reported for Afghan or international troops in Wednesday's fighting, it served as a reminder of the upsurge in violence predicted by many as the weather warms and the additional U.S. forces continue to move into areas they previously had not operated in.

In the largest battle, a convoy of Afghan police and forces with the U.S.-led coalition came under fire from multiple sides during a patrol in southern Uruzgan province, the statement said. The troops fired back and called in air support, killing 23 insurgents.

Nine militants were killed when troops came under attack during a search operation in neighboring Helmand province, and another 10 in fighting that broke out southwest of Kabul when international and Afghan forces attacked compounds believed to belong to Taliban operatives, the coalition said.

Wednesday's series of clashes came as Germany's foreign minister met with Afghan officials in the capital. Though Germany's 3,750 troops serve in Afghanistan's relatively peaceful north, they also were hit by an attack Wednesday. A suicide bomber jumped in front of a German vehicle, wounding four German troops, the NATO-led force said.

Elsewhere in the country, four would-be suicide bombers died in southern Ghazni province when their explosives detonated in the house they were staying in, said Sayed Ismail Jahangir, spokesman for Ghazni's governor.

Jahangir said the men died Tuesday in what appeared to be an accidental explosion. He said the government had received reports that they were planning a suicide attack.