The worsening state of security in the Somali capital of Mogadishu has hindered the work of aid agencies trying to tackle "an unfolding humanitarian catastrophe" in the Horn of Africa country, a group of non-governmental organisations (NGOs) said.

"International and national NGOs cannot respond effectively to the crisis because access and security are deteriorating dramatically at a time when needs are increasing," 40 NGOs said in a statement issued on 30 October.

"There is an unfolding humanitarian catastrophe in south central Somalia. Tens of thousands of people are currently fleeing violence in Mogadishu adding to the 335,000 people already needing immediate lifesaving assistance in Mogadishu and the Shabelle [Lower and Middle] regions," the statement added.

According to the NGOs, the parties to the current conflict and the international community have a responsibility to protect civilians, allow the delivery of aid and to respect humanitarian space and the safety of humanitarian workers.

Some of the major problems, the statement said, are harassment, intimidation, roadside bombs and landmines, as well as increased delays at checkpoints, where they have to pay to pass through.

"The purpose of the statement is to highlight how difficult it is to provide necessary assistance and the frustration of NGOs at not being able to respond adequately," said Réiseal Ní Chéilleachair, NGO Consortium focal point, on behalf of the NGOs.

In Mogadishu, there was relative calm for the second night following a weekend of furious fighting between insurgents and allied Ethiopian and government troops, which displaced thousands of families and claimed the lives of over 30 people.

A civil society source, however, said displaced families were afraid of renewed clashes and had not returned home. "I think for now many will stay where they think they will find a night of safety," he added.

Catherine Weibel, associate information officer for the UN Refugee Agency in Somalia told IRIN: "We now have preliminary reports that indicate about 35,000 people fled the city over the weekend."

Most of those leaving Mogadishu headed to the town of Afgooye, 30km south of Mogadishu, which was already struggling to cope with an earlier influx of up to 100,000 people who fled the capital earlier this year, the agency said.

Since intense fighting between Ethiopian-backed government troops and insurgents began in February, at least 1,000 people have reportedly been killed and more than 400,000 displaced.