The centre, set up by the Shanghai Co-operation Organisation, marked improving ties between its members, which include China and Russia.

The meeting has been held under very tight security, with a special zone set up to stop demonstrations.

One protest has already been stopped, and Human Rights Watch said political activists had been beaten up.

The BBC's Monica Whitlock, who is in the Uzbek capital Tashkent, where the anti-terrorism centre has been set up, says special forces armed with rifles stand on every main road.

SHANGHAI CO-OPERATION ORGANISATION China Kazakhstan Kyrgyzstan Russia Tajikistan Uzbekistan

The centre has been designed to act as a think tank for sharing information between member countries.

"One nation can't stand alone with the current threats," Kazakh President Nursultan Nazarbayev said.

The six members also agreed to help rebuild Afghanistan, whose President, Hamid Karzai, attended the talks.

"By helping Afghanistan, we are helping ourselves," said Kyrgyz President Askar Akayev.

Rights concerns

Our correspondent says Uzbekistan's handling of the talks has underlined how keen it is to prevent any signs of protest while Tashkent is in the spotlight.

According to Human Rights Watch, the police have broken up several protests against the Uzbek government of President Islam Karimov in the run-up to the summit.

Human Rights Watch said an officer from the counter-terrorism unit had warned one activist, a middle-aged woman, that she would have her legs broken if she picketed.

The next day she did attend a tiny rally and unidentified attackers beat her up, breaking her leg.

Unknown assailants also abducted and beat senseless a farmer who wore a T-shirt reading "I think the President should go, do you agree?".

They tied him up and dumped him unconscious in a remote spot outside Tashkent.

Afterwards, the farmer said he got an anonymous phone call threatening him that if the beating was not enough, his pregnant wife and children would be killed.

Human Rights Watch also documented two cases of children aged nine and 10 being detained.

The main reason the presidents are in Tashkent is to discuss their joint security.

Ensuring protection for freedom of speech and assembly, Human Rights Watch says, should be a key element towards promoting security in the region.