President Asif Ali Zardari has traveled to Dubai for medical treatment of a heart condition, spurring rumors of his resignation.
The president's spokesman on Wednesday called the reports "untrue" and "imaginary." He said Zardari's visit was a planned checkup.
Prime Minister Yousuf Raza Gilani's office said the president will remain under medical observation at a Dubai hospital in connection with symptoms related to a pre-existing heart condition.
In London, Pakistan's High Commission to Britain, Wajid Shamsul Hasan told the Associated Press that UAE doctors confirmed Zardari had a heart condition, but that it was not clear whether he had suffered a heart attack.
Zardari is expected to return to Pakistan soon.
The president is facing pressure from a memo scandal that led to the resignation last month of Pakistan's ambassador to the United States.
In October, Pakistani-American businessman Mansoor Ijaz publicly accused former Ambassador Hussain Haqqani of writing an unsigned memo requesting U.S. assistance to prevent a feared military coup in Pakistan. The letter was reportedly sent in May to Admiral Mike Mullen, the top U.S. military official at the time.
In return for U.S. help in preventing a military coup in Pakistan, the memo said a new national security team would conduct a full inquiry into allegations that Pakistan harbored terrorist leader Osama bin Laden. The new team also would hand over top al-Qaida members and ensure that Pakistan's military spy agency cuts ties to the Taliban, the Haqqani terrorist network and other groups.
Haqqani has denied any connection with the memo, and was replaced by former Information Minister Sherry Rehman.
Some information for this report was provided by AFP and Reuters.