YANGON, Myanmar — Opposition leader Aung San Suu Kyi was locked in a roadside standoff with police on Friday, running short of food and water and preparing to spend a second night in her car after being stopped while leaving Yangon.

It was the first time the 55-year-old Nobel laureate had tried to leave the capital since another standoff two years ago, which ended after 13 days when an increasingly poorly and dehydrated Suu Kyi gave up her protest and returned home.

Her party, the National League for Democracy (NLD), which won elections in 1990 by a landslide but has never been allowed to govern, said Suu Kyi and other NLD officials had been travelling in two vehicles when they were stopped by police on Thursday.

"They are running short of water and food today," the NLD's central executive committee said in a statement.

Witnesses said the group's cars were parked a short distance off the road south of Yangon where they were stopped. Nearby were an ambulance and police.

The NLD called on local villagers to provide Suu Kyi and her party with water and food.

In London, British Foreign Secretary Robin Cook said he deplored the treatment of Suu Kyi.

"We urge the authorities to lift these unnecessary and unlawful restrictions immediately, and call on the regime to open an immediate dialogue with . . . Aung San Suu Kyi and the NLD," Cook said in a statement.

The government confirmed it had stopped Suu Kyi but said this was for her own protection because her journey did not have "proper security arrangements."

"Security officials requested them not to proceed but stay in Dala town or return to Yangon. Due to threats of violence by armed insurgent separatist forces, travel by prominent persons to some parts of the country is at present inadvisable," it said.

"The government will take all necessary action in protecting her from these threats, while also safeguarding her human rights as much as possible, including the right to freedom of movement," it said.

Suu Kyi was under house arrest for six years until 1995 and her movements remain severely restricted.

In 1998 she twice spent several days in her car after being blocked by police when trying to leave Yangon.

In July 1998, a five-day standoff was forcibly ended by the military, and a month later she stayed in her car for 13 days on a road west of Yangon after being stopped by police and refusing government demands to return to the capital.

Suu Kyi said the military was trying to prevent her meeting supporters outside Yangon and was violating her freedom of movement. She ended the protest on August 24, exactly two years before she set out from Yangon on Thursday.

In a rare interview this week, Suu Kyi renewed her call for international pressure to help achieve democracy in Myanmar and said the recent opening of universities, closed in 1996 after anti-government protests, was a sham.

The government said it regretted her comments.