"Norway deeply regrets that Uganda's president today signed a new and stricter law against homosexuality," Norway's foreign minister, Børge Brende, said in a statement on Monday. "It will worsen the situation of an already vulnerable group, and criminalize individuals and organizations working for the rights of sexual minorities."
The new law strengthens the existing penalties for homosexual acts, with gay men now facing life imprisonment if arrested and found guilty.
Uganda's President Yoweri Museveni accused his Western critics of social imperialism as he signed the law into force on Monday in a ceremony on the lawn at the presidential residence in Entebbe.
"We are sorry that you live as you do, but we keep quiet about it," he said.
"It is a sad day for the gay community in Uganda, because this law will affect everyone," Julian Peppe Onziema, a local gay activist said.
Danish aid minister Mogens Jensen also signalled that Denmark would divert 50m Danish kroner of aid from government programmes
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Uganda has received around 6 billion kroner in aid from Norway since Museveni came to power in 1986. In recent years, the country has been giving about 400 million kroner per year.
Homosexuality is already illegal in Uganda, but the new law also makes it a criminal offence to sponsor or encourage homosexuality, or to fail to report any homosexual activity witnessed.