Russia plans to send another humanitarian convoy into eastern Ukraine "in the next few days", Foreign Minister Sergei Lavrov has said.

Mr Lavrov said the humanitarian situation there was "deteriorating".

Ukraine did not authorise the first convoy, which returned to Russia at the weekend, fearing it carried military equipment for pro-Russia separatists.

Ukrainian officials said a column of armoured vehicles crossed from Russia on Monday, sparking heavy clashes.

The crossing was reported close to the south-eastern Ukrainian city of Mariupol.

"The Ukrainian border has been breached by a convoy of several dozen tanks and armoured vehicles," security spokesman Leonid Matyukhin told Agence France-Presse.

"The convoy has been stopped by border guards... The battle is ongoing."

More than 2,000 people have died in recent months in fighting between Ukrainian government forces and the separatists. Some 330,00 people have been displaced.

The Russian and Ukrainian presidents are scheduled to meet in Minsk, Belarus, on Tuesday for talks on the crisis.

Mr Lavrov said he had sent a note to the Ukrainian foreign ministry on Sunday informing it of the new convoy.

He told a news conference on Monday: "The humanitarian situation is not improving but deteriorating.

"We want to reach an agreement on all conditions for delivering a second convoy by the same route... in the coming days."

Russia said the first convoy had delivered generators, food and drink.

Ukrainian sources said a column of about 30 armoured vehicles had entered from Russia close to the port city of Mariupol on Monday, bearing symbols of the self-styled Donetsk People's Republic.

Mariupol is in the hands of Ukrainian government forces, who ousted rebels in May.

When asked about the column, Mr Lavrov said: "I have not heard of this, but there is plenty of disinformation out there about our 'incursions'."

Ukraine and Western powers have accused Russia of arming the rebels, charges Moscow has denied.

There have been several previous reports of armoured vehicles crossing the border.

(BBC)