Japanese Prime Minister Junichiro Koizumi has visited a controversial war shrine in central Tokyo for the fifth time since taking office in 2001.
This is Koizumi's fifth visit to the shrine since taking office in 2001
The Yasukuni war shrine is seen by Japan's neighbours as a symbol of the country's World War II militarism.
Both China and South Korea voiced their anger at the visit, which they said would further strain relations.
Yasukuni honours Japan's 2.5 million war dead, including 14 convicted as criminals by a 1948 war tribunal.
"Koizumi must shoulder the historical responsibility for damaging Sino-Japanese relations," the Chinese ambassador to Japan, Wang Yi, said.
Built in 1869 to honour victims of the Boshin Civil War
Now venerates the souls of 2.5m of Japan's war dead
Those enshrined include 14 Class A war criminals
Mr Wang added the visit was a "serious provocation" because it coincided with the "glorious return" of China's second manned space flight, the Shenzhou VI, to earth.
South Korean Foreign Minister Ban Ki-moon for his part branded Mr Koizumi's visits to the Yasukuni shrine "the biggest stumbling block to South Korea-Japan relations".
"We strongly protest the visit to Yasukuni shrine despite our request and strongly urge that it is not repeated," he told the Japanese ambassador to Seoul, Oshima Shotaro, in front of reporters.
"It is not excessive to say that Prime Minister Koizumi's visits to the Yasukuni shrine have been the biggest stumbling block to South Korea-Japan relations," he added.
The BBC's Chris Hogg, in Tokyo says this was in some ways an unusual visit. Mr Koizumi turned up in a grey business suit, and did not change into traditional robes as he has on some occasions in the past.
He also did not enter the main hall of the shrine as he has in previous years, but prayed before it like any other worshipper.
Two weeks ago, a court in Osaka ruled that Mr Koizumi's visits to the shine violate the constitution, because they contravene the separation of state and religion.
But Mr Koizumi insists he is going as a private citizen and only wants to honour the millions of Japanese killed in the war and pray for peace.
The Japanese prime minister had previously visited the shrine four times since taking office in 2001.
He was last seen there in January 2004, but after his recent re-election many were expecting a new visit.