A top US envoy left Colombo on Thursday after castigating the government of President Mahinda Rajapakse for not delivering on promises to reduce violence while Britain also froze debt relief to its former colony.

Japan, Sri Lanka's largest single aid donor, was also planning to meet with international activists who are demanding the linking of aid to the island's human rights record, a diplomat, who declined to be named, said.

Human Rights Watch said it was encouraging Japan to be more pro-active in Sri Lanka.

"We expect them to take a leadership role in pushing Sri Lanka's government to end human rights violations," a spokeswoman for the New York-based rights group said.

The visiting US official, Richard Boucher, echoed the concerns of Sri Lanka's key aid donors last week.

"People are more fearful and face more difficulties," said Boucher, the US assistant secretary of state for Central and South Asian affairs.

"Overall there has been a deterioration in Sri Lanka's human rights record."

During his three-day visit, Boucher visited the besieged Jaffna peninsula where extra-judicial killings are rampant and heard the complaints of minority Tamils.