Pakistan's military said the Taliban has stepped up its campaign on security forces in North Waziristan, killing 12 soldiers and wounding 10 more in an ambush on an army convoy. The army said 10 militants were killed in the ensuing firefight. A purported Taliban spokesman, Ahmadullah Ahmadi, claimed responsibility for the strike. He told reporters by phone: 'We will keep on attacking the forces as long as the military continues operation in this region.' However, intelligence officials said 20 soldiers were killed in the attack and 35 were wounded. The army said in a statement another government soldier died in South Waziristan when militants launched a pair of attacks.