(Updates with quotes, background)
By Saud Mehsud
DERA ISMAIL KHAN, Pakistan, April 16 (Reuters) - The Pakistani Taliban have formally ended a 40-day ceasefire but are still open to talks with the government, a spokesman said on Wednesday.
Government negotiators were not immediately available to confirm if talks would continue.
Shahidullah Shahid said the insurgents were not extending the ceasefire, which began on March 1, because the government had continued to arrest people and had killed more than 50 people associated with the insurgency.
The government has also continued to carry our raids and had arrested more than 200 people, he said. Shahid also complained that unidentified Taliban prisoners had been tortured in prison.
"However, the talks will continue with sincerity and seriousness and in case there is clear progress from the government side, (the Taliban) will not hesitate to take a serious step," Shahid said in a statement.
Peace talks between the Taliban and the government began in February but the first round collapsed after less than a week because the Taliban bombed a bus full of police and executed 23 kidnapped men from a government paramilitary force.
The government suspended talks and threatened to launch a military operation against Taliban bases. Talks only resumed after the Taliban declared a ceasefire on March 1.
Since then, the government has released a few dozen low-level non-combatant prisoners, but the Taliban want hundreds of men released and the army to pull back from tribal areas bordering Afghanistan.
The Taliban have been fighting for years to overthrow the democratically elected government of Pakistan and impose strict Islamic law on the nation of 180 million people.
But in recent weeks fighting has broken out between rival Taliban commanders in the powerful Mehsud tribe. One commander wanted talks to continue but another is violently opposed. Around 50 people have been killed in the infighting so far.
The ceasefire did not ensure peace. More than 100 were injured and 34 were killed in two attacks in the capital of Islamabad during the ceasefire. Militants attacked a court and bombed a vegetable market. It was not clear whether a faction of the Taliban carried out the bombing or another of Pakistan's many militant groups.
The Pakistani Taliban are a loose alliance of militant groups separate from but allied to the Afghan Taliban.
Pakistani police have warned that the Pakistani Taliban are preparing to carry out devastating suicide attacks in the capital if the army moves against Taliban bases near the Afghan border. (Additional reporting by Syed Raza Hassan in Islamabad; Writing by Katharine Houreld; Editing by Alison Williams)