Pakistan's Prime Minister Yusuf Raza Gilani has appeared in the country's Supreme Court to face contempt charges.

Mr. Gilani arrived at the court Thursday under a heavy security presence, to defend his decision not to ask Swiss authorities to reopen a corruption case against President Asif Ali Zardari.

Mr. Gilani says President Zardari, as head of state, has immunity. Mr. Zardari is accused of corruption in a case that dates back to the 1990s.

On Wednesday, Mr. Gilani's lawyer told the court his client is not guilty of contempt.

The prime minister faces a jail sentence and removal from office if found guilty.

The court order escalates the pressure on Pakistan's civilian leadership, which faces separate court battles and high tensions with the country's powerful military.

A Supreme Court-appointed panel is investigating the origin of an unsigned memo in which Pakistan's civilian government allegedly asked for U.S. help in reining in the Pakistani military, following the U.S. raid that killed Osama bin Laden last May.

Last week, Mr. Gilani accused army chief General Parvez Ashfaq Kayani and Inter-Services Intelligence head Lieutenant General Ahmad Shuja Pasha of acting unconstitutionally by making unilateral submissions to the ongoing inquiry.

In response, the military said his remarks will have “very serious ramifications,” and it warned of “grievous consequences” for the country.