Mombasa, Kenya  - A German container ship released by Somali pirates after four months in captivity docked in the Kenyan port of Mombasa under tight security on Saturday.

The Hansa Stavanger, which was seized on April 4 off the Somali coast, spent the night at anchor outside the harbour and underwent a search for unexploded ordnance left behind by the pirates before tying up shortly after 2 pm (1200 GMT).

"I am a happy captain from an unhappy ship," the clearly elated captain, Krzysztof Kotiuk, told waiting media in the shadow of the hulking craft. "We are very tired after four months ... but it is very important that the crew is safe."

German Navy frigate the Brandenburg escorted the ship and its crew of five Germans, three Russians, two Filipinos, two Ukrainians and 12 Tuvalus from Somalia to Mombasa.

Torsten Ites, captain of the Brandenburg - which is part of the European Union's anti-piracy force Atlanta - said that the crew was doing well.

However, the Brandenburg had to provide medical and dental treatment to the seamen after four months of neglect at the hands of the pirates.

"They are slowly getting a smile back on their faces," Ites said. "Most of the crew had to sleep on the bridge ... and could not practice dental hygiene for four months."

"The pirates took away toothpaste and toothbrushes," he added. "They stole everything."

Some crew members told German media that they were subjected to fake executions and constantly had automatic weapons pointed at their heads.

Shortly after the ship docked, German federal police officials boarded to begin investigating what they deemed a "crime scene."

The crew was eventually loaded into waiting buses and driven past the media throng, smiling and waving for the cameras.

A German embassy official told the German Press Agency dpa that the crew would be kept in seclusion at a beach front hotel to relax while flights home were organized.

A new crew boarded, but the poor condition of the craft due to neglect meant that it was unclear when it could sail again.

"We have to check the damage and see what condition the ship is in," the Hansa Stavanger's new captain, Bernd Jantzen, told dpa.

The hijackers released the ship from its anchorage near the pirate haven of Harardhere on Monday after receiving a 2.7 million dollar ransom, a figure quoted by the pirates themselves.

The ship's owner, Hamburg-based company Leonhardt & Blumberg, has come under fire for giving in to the ransom demands and thus encouraging piracy.

Pirate attacks off the coast of Somalia continue to rise as young men look to make millions of dollars from shipping companies in ransom payments.

Some 42 vessels were seized in the Gulf of Aden and the Indian Ocean near Somalia last year. Already this year Somali pirates have seized 31 ships.

In a twist that highlighted the scale of the problem, the Stavanger docked in a berth vacated only hours before by the Maersk Alabama, the ship at the centre of a dramatic hostage drama earlier this year.

The Alabama's crew repelled a pirate attack in April, but their captain was then held hostage for five days on a lifeboat. He was freed when US Navy snipers killed three of the four pirates holding him.

The increase in hijackings has come despite the presence of dozens of international warships in the pirate-infested waters.

Ites, quizzed on why the pirates were not caught once they vacated the ship, defended the EU response.

"Twelve minutes after getting the call from the Hansa Stavanger captain, the EU force had assets in the area... we had helicopters, then 45 minutes later we had ships in close proximity," he said.

"The Hansa Stavanger was anchored very close to shore," he added. "When we arrived we did not see any pirate vessels in the water."

Peter Benn, a spokesman for Atalanta, said that the warships were making a difference. The rate of successful attacks has fallen from one in every three attempts to one in every nine in recent months, he said.

Piracy has been fuelled by insecurity in Somalia, where the weak central government is under attack by Islamist insurgents. Somalia has not had an effective government since the 1991 ouster of dictator Mohamed Siad Barre. (dpa)