PESHAWAR: The Pakistani Taliban warned the government on Tuesday they would punish any move to release Raymond Davis, a US consulate employee accused of murdering two Pakistanis in a case that has inflamed already strained ties with Washington.

US Senator John Kerry was due in Pakistan as part of the Obama administration's efforts to resolve the crisis.

Davis, the US consular employee jailed in Lahore for shooting two Pakistanis last month, says he acted in self-defence during an armed robbery.

Washington insists Davis has diplomatic immunity and should be released but the Pakistani government, fearful of a backlash from Pakistanis already wary of the United States and enraged by the shooting, says the matter should be decided in court.

“If (Pakistani) rulers hand him over to America then we will target these rulers. If Pakistani courts cannot punish Davis then they should hand him over to us,” said Azam Tariq, spokesman for the Tehrik-i-Taliban Pakistan.

“We will give exemplary punishment to the killer Davis.”

On Thursday, the United States is expected to present a petition to a Lahore court to certify that Davis has diplomatic immunity and should be released.

The warning from the al Qaeda linked Taliban, which has kept up suicide bombings to destabilise Pakistan's government despite several army offensives, underscores the charged atmosphere surrounding Davis' case.

Cash-strapped Pakistan, one of the largest non-Nato recipients of American military aid, is loathe to risk losing US support by keeping Davis in jail but also fears antagonising groups who see the government as a US puppet.

The issue has become a lightning rod for anti-American sentiment in Pakistan, which the United States counts as an important, if unreliable, ally in its war against militancy.

Davis' fate is certain to come up between Kerry, the influential chair of the Senate Foreign Relations Committee and member of President Barack Obama's Democratic party, in his meetings with Pakistani officials.

“Raymond Davis is not a diplomat but a US spy,” the Taliban spokesman said.

Supporters of the slain men have held protests and burned US flags. In addition to the two men Davis shot, a third man was killed when a US consulate vehicle, apparently trying to rescue Davis, struck and killed a passer-by.

Punjab Law Minister Rana Sanaullah said the provincial government sent the US consulate reminders that it should hand over the car and the driver who killed the man.