An online petition calling for the release of the BBC's Gaza correspondent, Alan Johnston, has now gathered more than 30,000 signatures.
There have been a number of protests in support of Alan Johnston
The reporter is presumed to have been abducted when he disappeared on 12 March after leaving his Gaza office.
UN Secretary General Ban Ki-moon has called for his immediate and unconditional release.
The BBC held a day of action on Thursday with al-Jazeera, CNN and Sky News joining a special live programme.
The unprecedented broadcast paid tribute to Alan Johnston's work and detailed the dangers for correspondents working in the Gaza Strip.
'Safe and well'
Mr Ban said Mr Johnston's coverage of Palestinian issues had won him a worldwide reputation.
He said freedom of the press should be protected "as a matter of principle".
The BBC's director general, Mark Thompson, met Palestinian Authority President Mahmoud Abbas who told him "he had credible evidence that Alan was safe and well".
But Mr Thompson said there had been no contact with any kidnappers and no demands had been received.
At a news conference in London on Thursday, Mr Johnston's parents appealed to their son's captors to immediately release him.
"You have family," said Alan's father, Graham Johnston.
"Please think about what this is doing to my family. Please let my son go now, today."
Kidnappers have abducted dozens of foreigners in Gaza, but none have been held for as long as Mr Johnston, missing for more than one month now.
The 44-year-old joined the BBC World Service in 1991 and has spent eight of the last 16 years as a correspondent, including periods in Uzbekistan and Afghanistan.
He has lived and worked in Gaza for three years and was the only Western reporter permanently based in the often violent and lawless territory.
His posting in Gaza had been due to end in late March.