TOKYO, April 10 (Reuters) Japan executed four convicted murderers on Thursday, the second group of inmates to be hanged this year, in line with Justice Minister Kunio Hatoyamas policy of reducing the number of prisoners on death row.

Numbers awaiting execution swelled to over 100 after a previous justice minister declined to sign execution orders because of his religious beliefs.

Those hanged on Thursday included 42-year-old Masahito Sakamoto, convicted of kidnapping and killing a 16-year-old girl in 2002, among other offences, the Justice Ministry said in a statement.

The executions bring to 10 the number of hangings under Hatoyama and come only two months after the last round of executions, an unusually short period in Japan.

“I have not paid any attention to the interval,” Hatoyama told reporters. “As justice minister, I am simply carrying out the demands of the law."

Japan executed nine people last year, the highest number since 1976, but well behind the United States, which executed 40 in the same period.

Amnesty International condemned the executions, saying they were an example of the “conveyor-belt” system Hatoyama had hinted at introducing when he suggested that the procedure for carrying out sentences should be simplified.

“This clearly shows that he aims to carry out large-scale executions,” Amnesty said in a statement. “Amnesty International strongly protests.”

In December the United Nations passed a non-binding resolution calling on member countries to suspend the death penalty with a view to abolishing it.

“There is a worldwide trend towards the abolition of capital punishment, but Japan is moving against the tide and with increasing energy,” Amnesty said.

Opinion polls show most Japanese support capital punishment.

Kaoru Akinaga, 61, who married and began writing poetry while on death row for fraud and two murders, was also among those hanged on Thursday.

“It was so sudden,” said Keiko Mitsumoto, who runs a poetry group to which Akinaga belonged and was in touch with him for years. “There is so much talk about abolishing the death penalty, I had hoped that he might serve life in jail instead.”

She said many of his poems referred with warmth to his family and home town in Hiroshima prefecture, southern Japan.

“Kaoru can also be a womans name and his poems are so gentle that I assumed he was female until I met him in jail,” she said.