Its militia captured another two towns - Tashqorghan and Samangan - in the northern province of Samangan on Wednesday, said Iranian radio, quoting a spokesman for the anti-Taleban alliance.

The BBC's Richard Galpin: "Another important military gain for the Taleban"

Earlier in the day, the Taleban was said to have taken over the strategically important border town of Hairaton, next to Uzbekistan.

Witnesses in Hairaton said the Taleban walked in without a fight to the undefended town on Wednesday morning.

Hairaton was a crucial supply route to Uzbekistan and a base camp for the anti-Taleban alliance and the opposition commander, General Dostam.

Independent sources also say that the Taleban have taken control of the strategic town of Pol-e-Khomri, which lies on the main road from the capital, Kabul, to the key city of Mazar-e-Sharif. But the opposition says it still has fighters in the town.

The Taleban have now made a clean sweep through north-west Afghanistan, including Mazar-e-Sharif, and Hairaton's fall brings Taleban control right to the edge of Central Asia and the former Soviet Union.

Russia said on Wednesday it was reinforcing defences along the borders of Afghanistan and its former Soviet allies.

"The situation is very complex and the danger to the frontiers of the CIS has increased," said defence minister Igor Sergeyev.

"Naturally we are taking every appropriate step to strengthen our contingent of troops," he said, referring to a 20,000-strong peacekeeping force Russia stations in Tajikistan. The Russian troops help patrol Tajikistan's borders.

Although Russia has no border with Afghanistan, it regards the former Soviet-Afghan frontier - running along Tajikistan, Uzbekistan and Turkmenistan - as its line of defence against the spread of radical Islam.

Fears and accusations

Tajikistan has expressed concern over the "escalation of military action" in Afghanistam but denied suggestions its forces had joined an anti-Taleban coalition.

But the Taleban said their fears about the threat posed by their advance were unfounded.

Russia says Pakistan supplies the Taleban with equipment

Earlier Russia said that the capture of the town of Taloqan in the north-east on Tuesday was achieved with Pakistani help - a charge the Taleban denied.

Meanwhile, Iran has said 11 Iranian diplomats and a journalist are safe and sound in the city of Kandahar, where it says the Taleban are holding them prisoner.

The Taleban have again denied the accusation.

After its military gains in the north, the Taleban administration in Kabul is renewing its bid for international recognition as the legitimate government of Afghanistan.

The Deputy Information Minister, Abdur Rahman Foteqi, said the Kabul government had the right to secure Afghanistan's seat at the UN after taking control of all the major cities in the country.

Pakistan Radio quotes him as saying recognition would allow an important oil and gas pipeline project from central Asia across Afghanistan to go ahead.

The Taleban is currently recognised as the legitimate Afghan government by only Pakistan, Saudi Arabia and the United Arab Emirates.

The rest of the world - and the UN - still recognise the ousted government of President Burhanuddin Rabbani.