By Katharine Houreld

ISLAMABAD (Reuters) - A teenager walked into a Pakistani police station on Friday and shot dead a 65-year-old man from a minority sect accused of blasphemy, their spokesman said, the second murder involving the country's controversial blasphemy laws in as many weeks.

Rights activists said the attack, and a spike in the number of blasphemy cases, was evidence of rising intolerance in the mainly Sunni Muslim South Asian state of 180 million people.

Victim Khalil Ahmad was a member of the minority Ahmadi community, a sect who say they are Muslim but whose religion is rejected by the Pakistani state.

Ahmad and three other Ahmadis had asked a shopkeeper in their village in central Pakistan earlier this week to remove inflammatory stickers denouncing their community, said Saleem ud Din, a spokesman for the Ahmadi community.

In retaliation, the shopkeeper filed blasphemy charges against the four men on May 12. Ahmad, a father of four, was in police custody when the teenage boy walked in, asked to see him, and shot him dead, Din said.

He said police told him that the shooter, a high school student, had been arrested.

Din said the lapse in security would have to be investigated. Pakistani police are notoriously poorly trained and security is often lax, critics say.

"They told us the person who shot Mr. Khalil is just a boy," Din told Reuters. "The hate campaign carried out against us by the mullahs is going on and on and on."

Khalil was killed in Sharaqpur police station, about 55 km (33 miles) northwest of the Punjab provincial capital of Lahore.

Ahmadis have been arrested in Pakistan for reading the Koran, holding religious celebrations and having Koranic verses on rings or wedding cards.

Some mullahs promise that killing Ahmadis earns a place in heaven and give out leaflets listing their home addresses. Four years ago, 86 Ahmadis were killed in two simultaneous attacks on Friday prayers in Lahore.

The Ahmadis consider themselves Muslim but believe in a prophet who came after Mohammed. A 1984 Pakistani law declared them non-Muslims, which makes them particularly vulnerable to the country's blasphemy law.

Story continues

The colonial-era law does not define blasphemy but says it is punishable by death. Anyone can file a blasphemy case claiming their religious feelings are injured for any reason.

The accused are often lynched, and lawyers and judges defending or acquitting them have been attacked. Rights groups say the laws are increasingly used to seize money or property.

Two politicians who suggested reforming the law were killed, one by his own bodyguard. Lawyers showered the killer with rose petals when he came to court.

The number of accusations is rising, according to a 2012 study by the Islamabad-based think tank, the Center for Research and Security Studies. In 2001, there was only one such complaint, but in 2011 there were 80.

No more recent figures are available but 2014 looks set to be a record. Earlier this week, 68 lawyers were charged with blasphemy at the instigation of a leader of a sectarian group that has been banned for militant violence.

They had been protesting against police violence and chanted the name of a policeman named after a companion of Prophet Muhammad.

Last week a prominent human rights lawyer defending a Pakistani university professor accused of blasphemy was shot and killed after being threatened in court by other lawyers.

Rashid Rehman had been representing the professor, who taught English and was accused by hardline student groups of making blasphemous remarks on his Facebook page in March 2013.

(Editing by Mark Heinrich)