NEW YORK - US newspapers Thursday regretted the abduction and killing of Pakistani journalist Syed Saleem Shahzad while underscoring the need for investigation in an effort to bring the culprits to justice. In an editorial, The New York Times said Shahzad knew he was a marked man, and paid tributes to Shahzads courage in covering issues relating to national security and terrorism. Suspicion inevitably falls on Inter-Services Intelligence, Pakistans chief intelligence agency, the Times said, while noting that ISI had issued a denial of allegations about its involvement in the murder. But the editorial said the denial was not enough. ISI Chief Lt Gen Ahmed Shuja Pasha, and his boss, Gen Ashfaq Parvez Kayani, the army chief of staff, must personally pledge a robust and transparent hunt for whoever was responsible. They must make clear to all who work for them that they will not tolerate attempts to silence reporters or anyone who dares to raise questions, it said. For the sake of justice, and the shredded credibility of Pakistans government, his (Shahzads) murderers must be found quickly and held accountable, the editorial said. Under Pakistans civilian government, journalists are freer to work than during the years of military dictatorship. Still, at least 16 have been murdered since 2002, making Pakistan the deadliest country for the news media last year, according to the Committee to Protect Journalists, it noted. Even as they mourned Shahzads murder, Pakistani journalists vowed they would keep doing their jobs. For the sake of Pakistan, we hope they keep up the fight. Noting that Shahzad made plenty of enemies in the government, The Wall Street Journal said his murder merits investigation, but its important to note that even more workaday journalism can be dangerous in Pakistan. In most cases, the government hasnt proceeded with investigations or prosecutions, the Journal said. The result is chilling: As one Pakistani writer put it this week, 'Murder is the severest form of censorship. Freedom House ranked Pakistans press freedom 134th among 196 countries this year.