Kenyan opposition leaders sought an injunction on Friday to block a press bill which contains a clause requiring reporters to reveal sources and has created a furore in a nation with one of Africa's strongest media.

Four prominent politicians, led by presidential hopeful Raila Odinga, took their suit to Nairobi's High Court to prevent publication of a bill critics say would be a return to the days of former president Daniel arap Moi when journalists were harassed and sometimes tortured. He left power in 2002.

"We are seeking ... (an) order to be granted restraining ... the Republic, Attorney General and Minister for Information and Communication from publishing the Media Act 2007 in the Kenya Gazette," said the politicians' suit.

The Media Bill has been passed by parliament and is awaiting President Mwai Kibaki's approval. But a host of media, church and civil society groups have urged him to send it back.

Under Kibaki, who took over after Moi's 24-year-rule, Kenya's media have enjoyed greater freedom and been robust in their criticism of the government.

Kibaki's government has, however, taken some steps against the media, including an armed raid on the second largest media house, the Standard Group, last year.

The government says the bill is merely intended to provide a legal framework for Kenya's media, similar to most liberal nations, as a safeguard against excesses.

The controversial clause in the bill states: "When a story includes unnamed parties who are not disclosed and the same becomes the subject of a legal tussle as to who is meant, then the editor shall be obliged to disclose the identity of the party or parties referred to."

Press freedom watchdog Reporters Without Borders said the bill would have "disastrous consequences for Kenyan democracy".