LONDON — Banks in the euro zone issued the lowest monthly volume of senior unsecured bonds in September since 1992, according to data-provider Dealogic.

Even for the region's biggest banks, the cost of selling this type of debt — a former cornerstone of long-term bank refinancing — climbed sharply as the sovereign-debt crisis escalated.

Amid rising funding costs, banks in Europe's currency bloc sold $7.1 billion of senior unsecured debt in September, the lowest since September 1992 when just $4 billion was raised, Dealogic said.

Issuance year-to-date has suffered as well. At $229.5 billion, the volume is the lowest since 2003, and down 29% since this time in 2010.

Deutsche Bank AG Thursday issued the first benchmark-size senior unsecured bond from a European bank in nearly three months. The EUR1.5 billion, two-year floating rate note was followed by a similar deal Friday from ABN Amro Bank N.V., which sold a EUR500 million, two-year FRN.

The other deals in Dealogic's September tally were under $500 million.

"Deutsche Bank paid up to reopen the senior market, but even here it is unlikely to see many others follow suit," said Societe Generale credit strategist Suki Mann.

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